tanzanite processing steps manual by eng gilayshamika

2009 Freelance Writing

Tanzanite Processing Steps at

Merelani Tanzania

FACE PICKING, ROM SORT RECOVERY, COBBING, CLARITY GRADING,

SIZING ONE, COLOUR GRADING, SIZING TWO AND CUTTING

Tanzanite the Uniqueness of Tanzania

Eng.Gilay Shamika2009

MINERALS AUDITOR IS

PRECISELY LIKE A

PILOT.

A SINGLE DISCREPANCY OF MINERALS WEIGHT WILL

CAUSE A HUGE TAX DEVIATION.

LIKEWISE

A SINGLE DISCREPANCY OF

A NEUTICAL MILE WILL CAUSE LANDING

DEVIATION

By Shamika, G.C

2009


1.0 INTRODUCTION ............................................................................................................................... 5

1.1 Mining ......................................................................................................................................... 5

1.2 Geology ....................................................................................................................................... 6

2.0 CLASSIFICATIONS OF TANZANITE GEMSTONES ............................................................... 7

3. 0 PROPERTIES OF TANZANITE GEMSTONES......................................................................... 9

3.1 Unique features of Tanzanite ................................................................................................... 9

3.2 Optical and other Properties of Tanzanite ......................................................................... 10

3.2.1 Optical Properties .............................................................................................................. 10

3.2.2 Physical Properties of Interest ....................................................................................... 12

4.0 FOUR (4) CS OF GEMSTONES ................................................................................................. 13

4.1Source of Colour in Gemstones .............................................................................................. 14

4.2 Presence of Different Colors in a Gemstone ..................................................................... 15

4.3 Gemstones Colour Fade up .................................................................................................... 16

5.0 TANZANITE PROCESSING METHODS AT TANZANITEONE ........................................... 16

5.1 Concept 1 ..................................................................................................................................... 16

5.2 Concept 2 ..................................................................................................................................... 17

5.3 Concept 3 ..................................................................................................................................... 18

6.0 DETAILED PROCESSING METHODS ..................................................................................... 20

6.1 Face picking ................................................................................................................................ 20

6.2 ROM Sort recovery .................................................................................................................... 21

6.3 Cobbing ......................................................................................................................................... 23

6.4 Clarity ............................................................................................................................................ 24

6.4.1 The meaning of An Inclusion ......................................................................................... 26


6.4.2Types of inclusions commonly found in Tanzanite gemstones and other gems

............................................................................................................................................................ 27

6.5 Grading the clarity of Tanzanite ........................................................................................... 27

6.6 Sizing Indicator .......................................................................................................................... 29

6.7 Sizing One (1) .............................................................................................................................. 30

6.8 Colour grading ............................................................................................................................ 31

6.8.1 GIA Colour grading steps ................................................................................................ 33

6.8.2 TanzaniteOne Colour grading steps............................................................................. 34

6.9 Sizing two (2) ............................................................................................................................... 35

7.0 GEMSTONE TREATMENTS, ENHANCEMENTS, AND CARE .......................................... 36

8.0 GEMSTONES CUT AND POLISH .............................................................................................. 37

8.1 Cutting Techniques ................................................................................................................... 37

9.0APPENDICES .................................................................................................................................... 38

Appendix 1: Birthstones & Anniversary Gemstones ............................................................. 38

Appendix 2: Anniversary Gemstones .......................................................................................... 39

Appendix 3: Weekday....................................................................................................................... 40

10: REFERENCES ................................................................................................................................. 41


Preface

It is not easy and will never be easy learning through

internet and practice. There is a need to stay in classroom

and learn about the gems for the benefit of my country.


1.0 INTRODUCTION

Tanzanite was formed over 600 million years ago when Mt. Kilimanjaro erupted caused a unique set of conditions to form deep within the earth - heat and pressure mixed with rare chemicals such as Vanadium to allow this exceptionally rare gem stone to form. These conditions remained constant for the entire 600 million years and Tanzanite grew. It was first discovered by man in 1967 when an enormous grassfire swept the land below Kilimanjaro Mountain. As Tanzanite is a brownish color in its rough state, the crystals lying on the surface were never noticed until when the grassfire had burnt the land and heated the stones. They turned bright, glittering violet-blue in the sunlight and attracted the attention of some Maasai tribesmen.

Tanzanite was named by Tiffany & Company (New York) and for the first ten years after its discovery Tiffany's had the exclusive right to this lovely gem stone. Today, after the liberalization of the Tanzanian economy, it is a free market.

To date the only known reserve of Tanzanite gemstone in the world is a strip of

8km by 1km at Merelani area in Manyara region, Northern of Tanzania. Tanzanite is

believed to be discovered at the area in 1967 and in 1971, the tanzanite mines were

nationalised and mining was taken over by the State Mining Corporation, STAMICO.

Production records for the first five years indicate a decrease in grades, mainly

attributed to haphazard mining and theft. During 1978, Tanzania Gemstone

Industries, a state organisation established by STAMICO, published a report

recommending the viability of full scale mining of gemstones. No meaningful action

was taken. During the next ten years, production decreased. There was also an

increase in informal, artisanal mining. By 1989, an estimated 30,000 artisanal miners

were working in the area.

In 1990, the Tanzanian Government curbed artisanal mining and demarcated

the area into Blocks A, B, C and D. Block A was awarded to Kilimanjaro Mines

Limited, Blocks B and D to small-scale miners and Block C to Graphtan Limited, a

graphite mining company. Graphtan ceased mining activities in 1996 and Afgem

acquired the mining licence for Block C. In 2000, Afgem completed a feasibility study

for the commercial mining of tanzanite and mine development commenced in 2001. In

2004, the TanzaniteOne Group acquired Afgem's tanzanite business and assets.

1.1 Mining

The mining method employed at TanzaniteOne mining Ltd is Underground

Mining. Currently there are six operational shafts in their SML which stretch by 1km

by 2km. These operational shafts are ; Bravo shaft, CT shaft, Main shaft, Askari shaft,

Delta shaft and Investor shaft which is used as hoisting shaft for Main shaft, Delta

shaft, and Askari shaft to bring out ores. Two shafts TC and JW are not operational.

Mining currently takes place through five shafts: Delta, Askari, Main, CT and Bravo


shafts. Shafts are sunk at an angle of 42 along dip of the JWZ mineralisation zone.

The shafts are fitted with tracks and material is removed via a hoist and inclined shaft

structure. Drives are driven along strike at an angle of 16 along the plunge of the

fold noses. A monorope (endless looped rope and pulley) system is used to remove

materials in bags from the mining fronts towards the inclined shaft ore pass

infrastructure. Blasting is used as the main method of mine advancement. Once

favourable boudin structures are approached pneumatic drilling and handpicking is

used to remove tanzanite as carefully as possible.

1.2 Geology

Tanzanite is a thousand times rarer than diamonds and is trichroic, which

means that in its rough form, it radiates three different colours from each of its

crystallographic axes: blue, violet and burgundy. Tanzanites are found in Lelatema

Antiform in Merelani, Manyara Region, Northern Tanzania. It is believed to be formed

600 million years ago.

3Tsavorite + H2O + 5CO2 = 2Tanzanite + 3Quartz + 5Calcite

Tanzanite is found within a relatively complex geological environment and is found in

'chocolate-tablet' boudin structure, typically located in the hinges of isoclinal folds

(folds dipping in the same direction) present in the ore body. The Geologists at

Tanzanite one has identified two potential strips of these unique zones in the area and

has named them as Upper Horizon and Lower Horizon. The familiar and currently

mined is the JW zone in Lower horizon, named after Ally Juyawatu who is believed to

be the first miner in the area. Deep hole drilling, geophysics, geochemical analyses

and structural and geological mapping have all increased the level of geological

knowledge. Drilling programme has shown that the lower horizon, which hosts the

economic mineralisation, extends three times further dip than initially anticipated.

This databank of proprietary geological know-how is unrivalled and will become more

important than ever as mining operations deepen and the artisanal mining styles

employed on the other license blocks become redundant.


2.0 CLASSIFICATIONS OF TANZANITE GEMSTONES

The gemstones are classified according to the clarity (the extent of inclusion free) and

colour. There are standards used to explain the inclusion effects on the gems quality

set by GIA. For Tanzanite gemstones, the TanzaniteOne Mining Company has its own

standards special for Tanzanite. Let us start by looking on them before we go into

classifications. Just the abbreviations and what they mean but you will broadly have

full dose of Inclusions on the section of Clarity grading. (Table 1, 2 &3)

Table 1: GIA Standards

Inclusion Abbreviation Explanation/What is seen in Gems

VVS Very Very Slight

VS Very Slight

SI1 Slight Included 1

SI2 Slight Included 2

I1 Included 1

I2 Included 2

I3 Included 3

Table 2: TanzaniteOne Standards

Colour and Inclusion Abbreviation

Explanation/What is seen in Gems

A Exceptional Colour, Eye Clean

B Rare Deep Blue/other Colour, Eye Clean

BSI B Colour-Slightly Included

BI B Colour Included

BL B Lighter Colour Grade, Eye Clean

BLSI B Light-Slightly Included

BLI B Light Included

D Opaque Material(agreed to use D instead of O )


Table 3: The effect of Inclusions on the types of Gemstones

Type of Gemstones Inclusions Effect

Type 1 Gemstones

VVS minute to not detectable

VS minor

SI1 NOTICEABLE to obvious

SI2 OBVIOUS to noticeable

I1 prominent to moderate effect on appearance or durability

I2 prominent to severe effect on appearance or durability

I3 prominent to severe effect on beauty, transparency, or

durability

Type 2 Gemstones

VVS minor

VS NOTICEABLE to obvious

SI1 noticeable to OBVIOUS

SI2 obvious to prominent

I1 prominent - moderate effect on appearance or durability

I2 prominent - severe effect on appearance or durability

I3 prominent - severe effect on beauty, transparency, or

durability

Type 3 Gemstones

VVS NOTICEABLE to obvious

VS noticeable to OBVIOUS

SI1 obvious to prominent

SI2 obvious to PROMINENT

I1 prominent to considerable effect on appearance or

durability

I2 prominent to severe effect on transparency or durability


I3 prominent to severe effect on beauty, transparency, or

durability.

3. 0 PROPERTIES OF TANZANITE GEMSTONES

Tanzanite is an exceptionally rare gem stone- estimated at a thousand times rarer than diamond. There is only one source for it in the world - on the slopes of the

legendary Mt. Kilimanjaro at Merelani Tanzania.

3.1 Unique features of Tanzanite

Tanzanite is among the few gem stones in the world that are "trichroic". This means that when white light passes through, it breaks into 2 paths and creates 3 different colors - one axis will look violet, reddish brown and the third a blue-violet. The picture below shows the same Tanzanite crystal from 3 different angles showing its

amazing trichroism.

Figure 1: Three colours of Tanzanite in response to light

In the rough state most Tanzanite is predominantly brown and blue. Heating at 600 degrees centigrade causes this color to change to blue violet. This is a permanent and stable change. Tanzanite due to its trichroism characteristic has never been

synthesized, but a number of imitations exist and the most common is blue-violet glass. A synthetic fosterite has also been used as an imitation and is known as Tanzanique in the trade. It does not have the same trichroism so is easily distinguished from the real Tanzanite.


Table 4: Gemological Properties of Tanzanite Gemstones

Gemological Properties Unit of Measure

Gem Species Zoisite

Specific gravity 3.35

Hardness (Mohs Scale) 6.5

Toughness Fair

Stability to light Stable

Carat Weight Below 1-10 ,rarely 100

+

Birthstone December

A great deal of Tanzanite marketing makes a big deal of the "red flash" phenomenon of Tanzanite. This is one of the features of the stone and is due to Tanzanite's trichroism. Tanzanite is extremely light sensitive, with incandescent lighting (yellow lighting found in common light bulbs) tending to shift its color to the violet side causing the red and pink flashes to appear within the stone. The images below of the same stone show it under white (daylight) and under incandescent light:

Under white light

Under incandescent light

3.2 Optical and other Properties of Tanzanite

This is very important to be pinpointed particularly by Clarity and Colour graders of

the Tanzanite. Is through these properties one can master the colour and clarity

grading. Knowing how the light breaks down into spectral colours through the

Tanzanite gem will help the colour and clarity grader where to focus (the position of

eyes) during grading. Therefore kin observations of these optical properties will pave a

way for real gems valuation rather than being on the eyes of beholder.

3.2.1 Optical Properties

The optical properties are the major properties of gemstones which distinguish them

from precious metals/minerals which are completely opaque in response to light.

The figures below (Figure 2 & 3) show the optical properties of Gemstones in response

to white light when passes through;


Dispersion: This is the splitting of light as it enters a gemstone. Colors separate

during refraction of white light, which leads to seeing fire in a gem. By this

property, the internal features of the gem can be identified and hence used as a

distinguishing feature from other gems classification. The dispersion index

differs from gem to gem due to anatomy of each type of gem and inclusions

found within a gem type.

Refraction: The bending of light (or any wave phenomenon) when it moves

between media with different conductive velocities. Refractive Index is the ratio

of the velocity of light in a vacuum to that in the substance; it determines the

angle at which light bends when it enters a substance obliquely.

Double Refraction: A phenomenon which occurs when the ray of light entering

a crystal is refracted and divided into two rays instead of one. This is most

commonly seen in Calcite and Zircon.

Luster: The manner in which a mineral/gemstone reflects light from its

surface; it is affected by the surfaces smoothness and reflectivity. Rough and

polished tanzanite will respond slightly different;

Figure 2: Dispersion of the original white light through a prism.


Figure 3: Dispersion of the original white light through a gemstone.

Points to ponder from above:

In a gem the dispersion occur parallel to the source of light with different direction to each other and;

Dispersion occurs in the same side of source of light.

Note: These optical findings are very important properties to identify where to watch the colors of the gem relative to the source of light; they provide the location of eye and identification of number of colours in a gem.

3.2.2 Physical Properties of Interest

Gems are subjected to treatments and enhancements for quality improvement.

Heating, Cutting and polishing are the methods used for quality improvements. These

can only be done after studying the physical properties of the gem concern otherwise

the treatments and enhancements cant be achieved.

Cleavage: The tendency of a mineral /gemstone to break along a plane due to a

direction of weakness in the crystal. Minerals and gemstones can be split along

certain flat planes which are called cleavage. Cleavage is related to the lattice

(the cohesive property of the atoms) of the crystal.

Fracture: A break with an uneven or irregular surface crack.


Tenacity: The strength of a mineral/gemstone. It is also its resistance to breaking, crushing, bending, crumbling, tearing, or changing shape. There are several different terms used to denote a minerals tenacity. They are listed below.

-Elastic: It can be bent and will resume its previous shape when let go.

-Ductile: It can be pulled and made into very thin threads.

-Flexible: It can easily be bent without breaking and can be shaped.

-Fragile: It will easily break into pieces.

-Friable: It crumbles easily.

-Malleable: It can be flattened out into thin sheets without breaking.

-Sectile: It can be cut into shavings with a blade.

The above optical and physical properties are extremely important for all concerned

with gemstones to know the different values and measurements of gemstones. Without

knowing these values, it would be extremely difficult for anyone to be able to identify

one gemstone from another.

4.0 FOUR (4) CS OF GEMSTONES

The Colour, Clarity, Carat weight and Cut are termed as 4cs of the gemstones. These

are the factors used for grading the quality and price of the gemstones.

Color is the main indicator of value of Tanzanite, the more vivid pure and

bright a color is, the more it is valued. Tanzanite exists in three different

colours when subjected into natural light or fiber light. But with a single glance,

it appears predominantly brown and Blue-violet into light. However when it

comes into colour grading, colour remains a subjective "eyes of the beholder"

sensation. The most colorful Tanzanite is graded as AAA grade for GIA

Standards and A grade for TanzaniteOne Standard.

Clarity is a major factor in determining quality and, consequently, the value of

a gem. This refers to what extent the gemstone is flawless or clear without

inclusions. The more the gemstone is clear (without inclusions) the more the

value of the gemstone. Inclusions not only distract the eye, but interfere with

the behavior of light in the gem, and have a significant effect on brilliancy.

However; inclusions that do not affect the durability of colored are not an issue

in determining value as corresponding inclusions in diamonds.


Carat weight is the international standard unit for gemstones. All gemstones

price is based on carat weight. One carat (1Ct) equals to 0.2g.Tanzanite is

almost found in the range of 1-10 carats but rarely up to 20-100+ carats.

Cut has the least impact on a value of the gems among other 4 C's although

due to competition with other gems with posh cuts, the cut of Tanzanite is

important to add value. Cut shapes and cutting techniques will be discussed in

the Cutting section.

4.1Source of Colour in Gemstones

Color results from a minerals chemical composition, impurities that may be present, and flaws or damage in the internal structure. Most minerals are usually white or colorless in a pure state. Many impurities can color these minerals and make their color variable. Some crystals get their color from growth imperfections. Growth imperfections interfere with light passing through the crystal making it appear darker or nearly black.

Idiochromatic minerals are "self colored" due to their composition. The color is a constant and predictable component of the mineral.

Allochromatic minerals are "other colored" due to trace impurities in their composition or defects in their structure. In this case, the color is a variable and unpredictable property of the mineral.

Pseudochromatic minerals are "false colored" due to tricks in light diffraction. The color is variable but a unique property of the mineral, such as the colors produced in precious opal and the shiller reflections in Sunstone and Labradorite.

The most common trace elements/coloring elements in minerals are: Beryllium, Chromium, Cobalt, Copper, Iron, Lithium, Manganese, Nickel, Sulfur, Titanium,

Uranium, and Vanadium.


4.2 Presence of Different Colors in a Gemstone

Color is the most important characteristic of tanzanite gemstones. For the Diamonds it is the absence of color which is most important.

Light absorption and Trace elements are most factors for having different colours of gemstones;

Color is produced by the way a gemstone absorbs light. Light is an electromagnetic vibration at certain wavelengths, but the human eye can

only perceive certain wavelengths. There are several different reasons why

the various gemstone varieties absorb light differently. Some gemstones are said to be idiochromatic or self-colored. They absorb certain wavelengths of light due to characteristics of their chemical structure. Most gemstones are allochromatic. They are colored by impurities or trace elements in their crystal structure.

The relationship between a chemical impurity and a gemstone color is not a simple one. Sometimes a similar color can result from different trace elements. Also, a single trace element can produce different colors in different gem varieties. This is because there is a complex relationship between the gem's crystal structure and the trace elements.

Another way in which gemstones acquire color is through human intervention in the form of gem treatments. Heat treatment is often used to change the chemical state of

an impurity to deepen or lighten color, reduce a certain hue, or improve clarity. Gemstones are also dyed, treated with chemicals, coated with chemicals or metals, irradiated, and artificially colored in many other ways to alter their appearance. All gemstone treatments must be disclosed by the vendor prior to the sale of the gemstone.

Through my experience as a Senior Minerals

Auditor (TMAA) at TanzaniteOne I have

observed the following by using fiber light;

If all the different wavelengths of light pass

through a gemstone, it appears colorless.

On the other hand, if the gem material

absorbs all the light, it attains maximum

intensity of its colour (extremely deep/Black)

and;

If a stone absorbs all wavelengths except

those in the red part of the spectrum, the gem

appears red.

The literature also supports these

observations. The effect depends on the

intensity of light applied (Incandescent lights

6200K onward)


4.3 Gemstones Colour Fade up

The colors of some minerals and gemstones can be altered by time or exposure to sunlight or bright display lights. Some may fade, while others may oxidize. Some porous gems, such as Agate, Lapis Lazuli, Pearls, and Turquoise may be treated to stabilize their color. Gemstones that have had their color altered through the various treatments may also fade, change color, or become spotty over time.For tanzanite is not the case. The colour attained by heat treatment that is Blue Violet is a permanent change. Even the brown colour which is predominant at its ground state does not fade at all. It only changes when subjected into heat to blue violet.

5.0 TANZANITE PROCESSING METHODS AT TANZANITEONE

The discussions will be based on the methods used for Tanzanite gemstones processed

at TanzaniteOne. The prime methods are underway in the Sort house and other

methods that are cutting and polishing carried in Cutting house. The discussion and

explanations will base on experience grabbed in Sort house. Probably next compilation

will include everything done in cutting house-Cut, pre-formed and polishing. But in

this compilation, cutting methods and shapes will only grossly highlighted.

Before going into processing methods, it is healthiest to renaissance three concepts to

bring in perfect understanding when discussing those methods practiced at

TanzaniteOne. I have conceptualized a figurative imagination to enhance

understanding of the gemstone processing methods.

(Therefore the Concepts below are subjective to Compiler and not referred from

anywhere)

5.1 Concept 1

TanzaniteOne not only produce Tanzanite but also Tsavorite and other Coloured

gemstones. Therefore bear in mind, you will find other gems and not Tanzanite only

and;The Colour referred is Blue even for those which are not blue are named after it.

The table below justifies the said.


Table5: Colour coding at TanzaniteOne

COLOUR EXPLANATION

A Exceptional Colour, Eye Clean

B Rare Deep Blue/other Colour, Eye Clean

BSI B Colour-Slightly Included

BI B Colour Included

BL B Lighter Colour Grade, Eye Clean

BLSI B Light-Slightly Included

BLI B Light Included

D Opaque Material(agreed to use D instead of O )

5.2 Concept 2

Try to imagine gemstone is like a Pineapple in which the first step is to pick it (face

picking) from the market wash it (Sort) start peeling (cobbing), Cut it (sizing one) up to

the last stage of the pineapple peeling and cutting which you remain with inner rod

like feature protruding at the bottom where you hold (Sizing two).OR Imagine the

Pancake being cut symmetrical inwards until you leave the last portion at the middle.

Assimilate above scenarios with the Tanzanite processing methods-The gemstones are

brought (face picking) from the mining site/shaft to the Sort house for processing.

Each step reduces the gemstones (like pineapple example) up to the last step (sizing

two) where you get minimal Sizes. Observe the diagram below for support;

Face picking being the first method where you have large gemstone (the whole

pineapple) and the last stage is Sizing two (nice pieces of pineapple with different sizes

ready to eat)


Figure7: Concept on Size reduction related to Gemstones processing steps.

5.3 Concept 3

From the above concepts, carry on thinking the example of pineapple. From pineapple

you will have materials (peels and rod like at the middle) to be discarded and those for

eating. But due to massive demands of materials for production in different sectors,

these days nothing is discarded.

The same happen in gemstone processing methods. Along the processing methods,

there are materials of irrelevant but are then sold locally. The processing methods are

summarized below in Table 6 with the explanation of what is left and what is

seconded in the next or iteration stages.

1. Face Picking

2. ROM sort rrecovery

3. Cobbing

4. Clarity grading

5. Sizing One

6. Colour grading

7. Sizing Two


Table 6: The Gemstone processing material balance

PROCESS/METHODS CARRYOVERS /LEFTOVERS

Face Picking

The gems are picked from the shaft just by looking on the face of it and

identify it. They are normally large stones. Those which are clean go to cutting

section and those which are attached or embedded to normal stones; they

have to be brought in the sort house for sort recovery and the rest of the

methods.

Romsort Recovery The process of sorting materials from the run-of-mine and discord unwanted

materials. The recovery gems are then seconded to cobbing.

Cobbing

Gems from ROM Sort recovery are cobbed and graded into A-C, D grade,

Colour, Tsavorite, Waste and Off-Cuts.

Carry Over: A-C carried to Clarity grading while Coloured (greenish gems) are

taken to Cutting process or sold as they are.

Left Over: D grade, Coloured, Tsavorite, Waste and Off-cuts are collected for

local selling and sometime for export.

Clarity Grading

A-C gems from cobbing are clarified into A, B, BL and SI, I.

Carry Over: A, B and BL gems are carried to colour grading without passing

into sizing 1. While SI and I gems are carried out into Sizing 1

Left Over: Nothing left here, all materials are in transit

Sizing One

SI and I gems from Clarity section are sized into ranges from size 1 to 14. At

sizing 1, the gems with the weight from 0.01 up to 0.49grams are arranged

here and those above, from 0.5 up to 20+grams are taken to Sizing 2 for more

weight arrangements.

Carry Over: SI and I Gems with size 5 to size 14 are carried to Colour grading

while;

Left Over: SI and I Gems with size 1 to size 4 are collected ready for selling.

Colour Grading

At this section remember we have A, B and BL gems from Clarity section and

also SI and I Gems with size 5 to size 14 from sizing 1 section carried to Colour

grading. Therefore these are our feed to be processed. The common useful

methods used for colour grading is from GIA (Gemology Institute of America).

Carry Over: The colour of A, B and BL gems are enthusiastically confirmed

while SI and I Gems are classified into relation to A,B and BL to get their

hybrid i.e. A(I),A(SI),AL(I) and AL(SI) but these have never been obtained.


Therefore only BI, BSI, BLI and BLSI are graded from SI and I. That means

broadly there will be A, B, BL, BSI, BI, BLSI and BLI. But grossly colour

grading can end at A, B, BL and C. That means all gems with inclusion are

generalized as C (BSI, BI, BLSI and BLI)

Left Over: No materials are left here. All colour graded gems are carried to

Sizing two.

Sizing two

The intention of this section is to grade the gems according to their weight

starting from Size 5. We already have colour grading; the last stage is to

arrange those gems with reference to their weight and colour. The gems with

the same size and colour are mixed together and weighed.

This is the last stage where the gemstones after being sized according to colour

and weight, they are packed ready for selling.

The detailed explanations will include the vivid example of what is done in all

methods at TanzaniteOne Mining Company.

6.0 DETAILED PROCESSING METHODS

The whole seven (7) processing methods undertaken at TanzaniteOne will be discussed

with detailed example for each method.

6.1 Face picking

The gems are picked from the shaft just by looking on the face of it and identify it.

They are normally large stones, medium and small. They comprise wanted and

unwanted materials. All materials are brought in the Sort house for clean up and

weighing. Those which have no inclusion, the decision need to be made whether to sell

as they are or go to cutting and those which are attached or embedded to normal

stones and inclusions, they have to remain in the sort house for sort recovery and

other processes. These are like alluvial gold (course particles of gold) picked from Ores

or collected on gravity circuit (free/liberated gold).Table 7 shows the practical example

of face picking;


Table 7: Practical example for Face picking

Total weight Picked from Pit (g)

Total weight of grade D (g) Total weight for cobbing (g)

Shaft

10383.99 4616.04 4567.95 MAIN

Source: TMAA

Explanation based on the above practical example

Total weight Picked from Pit: This is the total weight of materials picked from

the pit. They are picked by the miners just by looking and find them as the

gemstones and packed into bags, all the way to Sort house.

Total weight of grade D: The materials from the pit are then checked for

confirmation. They have to be washed to see them clearly. Those which are

Opaque are the ones called grade D and the other which are transparent and

pass the light by showing their true colour, are the real gemstones separated for

cobbing. Hence total weight of D grade means the weight of Opaque materials.

They are gemstones with less value. They dont exhibit the true properties of

tanzanite.

Total weight for cobbing: This is the weight of real gemstones to be taken to

the next process of cobbing. The real gemstones are cobbed to remove

unwanted materials attached to them. But also reduces the gemstones into

reasonable sizes to ease clarity and colour grading.

Shaft: This is the area where those materials have been picked/ mined. It is

called shaft because the place is underground where you need to descend by

shaft. Therefore the mining area is named after it. In this example the

gemstones were brought from Main Shaft.

6.2 ROM Sort recovery

This is the process of sorting/separating materials from the run-of-mine (ROM).It is

the same as face picking logically but the difference is;

ROM is the pile of materials (ores) with general geological estimation of grade

e.g. 5g/t. That means for every tone there is 5gram of required

gemstone/minerals.

The second difference from face picking materials is that, the materials from

ROM need to be crushed to the required size before brought in the Sort house

for sorting i.e. separation of gemstones, D grade and other Taka Taka.


The Crushed materials from ROM are stored into bags and drums. Sorting is

done by taking substantial portion of materials depending on the number of

Sorters.

To avoid direct contact of materials for security purposes, the sorting and all

other methods are done in the housing cabins.

Table 8: Practical example for ROM Sort recovery

Total weight from ROM( g) Total weight recovery (g)

147100 gm 10764.20gm

Explanation based on the above practical example.

Total weight from ROM: This is the weight of portion of ROM materials given

to sorters on a particular day for sorting required and unwanted materials.

Total weight recovery: This is the weight of required materials (recovery)

obtained from ROM materials.

Therefore ROM sort recovery is the process of separating gemstones and other

materials from the process plant crusher brought by conveyor. The separation/sorting

is done manually. For gold the crushed materials from the mill go into cyanidation and

leaching BUT for gemstones the crushed materials are then sorted by hand to get the

gemstones. (Figure)

Figure 8: ROM Sort recovery process. The spatula-like equipment is used for sorting

rather than fingers for security purpose.


6.3 Cobbing

Is the trimming of gemstones to remove unwanted materials and to reduce the gems

into reasonable sizes for easiest of undertaking clarity and colour grading.

The small whippy hammers are utilized delicately to remove unsatisfactory materials.

Despite the loss of weight necessarily incurred in the cobbling process (off cuts), the

remaining material is upgraded to such an extent that it brings a price more than the

original gems and makes up for the weight loss and cost of labor. Let us remind

ourselves about the following which had already previously discussed;

Remember from face picking and ROM sort recovery, required materials were taken to

this stage. In previous pages we have mentioned that at TanzaniteOne not only

tanzanite is available but also other gemstones. The practical example below depicts

the gemstones available-Coloured gemstones, Tsavorite gemstones which is also

available at Kenya Tsavo national park and is named after it.

Table 9: Practical Example for Cobbing

Total weight(g) A-C D grade Coloured Tsavorite Waste Off-cut Total weight(g)

10701.5 1805.35 5160.94 334.78 53.89 334.39 3009.53 10698.88


A-C: TanzaniteOne during Cobbing they combine all gemstones with inclusions

and name them as C grade. Therefore whenever you see Colour grade C it

means the whole package of BSI, BI, BLSI and BLI.

Therefore in practice A-C means combination of all colours A, B, BL, BSI, BLSI,

BI and BLI (revise colour grading standards at TanzaniteOne pg)

Coloured: These are the gemstones available at TanzaniteOne which do not

have the real colour of tanzanite.

Tsavorite: Tsavorite gemstones are also available at Kenya Tsavo national park

and are named after.

Off-cut: These are small pieces of all gemstones available during

hammering/cobbing of gemstones. They are used for mixing with other

materials to make Tiles and other ceramic items for shining the surface.


Figure 9: The cobbing process at TanzaniteOne.

6.4 Clarity

Clarity is the second most important of the 4c's when considering Tanzanite quality.

Clarity simply refers to how inclusion-free a gemstone is. Once again, the most

universally accepted and most documented system is the GIA system but there are

also numerous other trade based systems in use like the one used at TanzaniteOne as

seen in previous chapters. The other system commonly used is Munsel System but

will not be discussed, have a time to web it.

The discussion will only base on GIA system and its TanzaniteOne derivative system

for tanzanite. Below is a chart showing the GIA and TanzaniteOne clarity/colour

grading system which will be referred in our discussions. The TanzaniteOne

Standards is the one which is emphasized since we are deeply dealing with

tanzanite in our compilation.GIA system is revised for building the concept related

to TanzaniteOne Clarity/Colour grading standards. Figure. And Table 10 indicates

the level of inclusions and how those levels can be graded.

A B/BL BSI BLSI BI- BLI (TzOne System)

Figure 10: GIA and TanzaniteOne Clarity grading


Explanations of level of Inclusions

VVS: This is the top grade in the GIA system. Tanzanite is classed by the GIA as

a "Type 1" gem which means it is graded very strictly. Stands for Very very

slightly included and whilst most VVS Tanzanites are flawless they can contain

minute inclusions which are difficult to see with a loupe (10x magnification)

and invisible to the unaided eye. Typical minute inclusions may be very fine

needles, tiny hairline feathers, very faint clouds and percussion marks.

VS: This stands for Very Slightly Included and these stones are characterised

by minor inclusions which are somewhat easy to see under 10x magnification

but usually invisible to the unaided eye. Typical inclusions may be small

included crystals, liquid inclusions, fine needles, small feathers

SI1 - SI2: This stands for Slightly Included and these stones are characterised

by noticeable inclusions which are apparent under 10 x magnifications. In SI1

they are usually visible and SI2 quite visible to the unaided eye. Typical

inclusions are included crystals, large liquid inclusions, feathers, dense clouds.

I1-I2-I3: The lowest grade. Stands for Imperfect. These stones are characterised

by inclusions that have a negative effect on either appearance, durability or

both. At I1 there is a moderate effect on either factor, I2 a severe effect on both

factor and I3 a severe effect on both factors.

Table 10: The summarized level of inclusions

GRADE STANDARD WHAT YOU SEE

VVS

Very, Very Slightly included -

Inclusions are easily seen

under 10X magnification, but

usually not visible to the

unaided eye.

The gem is almost perfectly

transparent. If you examine

the stone closely enough, you

may see very tiny flaws.

VS

Very Slightly included -

Obvious inclusions are easily

seen under 10 x

magnifications, and usually

visible to the unaided eye.

The gem is still transparent

and lively. On close

examination, a few small

flaws can be seen.


SI 1

Slightly Included 1 -

Inclusions are large and

numerous under 10x

magnification, and prominent

to the unaided eye.

The gem is mostly

transparent, but one or more

flaws are easily visible.

SI 2

Slightly Included 2 -

Inclusions are large and

numerous under 10x

magnification, and very

prominent to the unaided eye.

The gem is generally

transparent, but has a

number of large flaws.

I 1

Included 1 - Inclusions are

very obvious and have a

moderate negative effect on

the appearance OR durability

of the stone.

The stone either has so many

inclusions that it is only

partly transparent, or if

transparent it has one or

more cracks that might

weaken the gem.

I 2



severe negative effect on the

appearance OR durability of

the stone.

The stone either has so many

inclusions that it appears to

be translucent, or if

transparent it has cracks that

could weaken the gem.

I 3



severe negative effect on

BOTH the appearance AND

durability of the stone.

The stone has so many

inclusions that it appears to

be translucent, AND it has

one or more cracks that

weaken the gem

6.4.1 The meaning of An Inclusion

The inclusions are virtually materials other than original gemstones. They may be formed before, after or on the same time with the gemstones. Broadly is defined as; Any irregularity or dislocations in a crystal's lattice, or structure, marks of the crystallization phases, color striations, and internal fractures, which may be caused by internal stress or external pressure.

Simply the material trapped within the body of a crystal which is different from the primary elements of the host crystal.


6.4.2Types of inclusions commonly found in Tanzanite gemstones and other gems

Crystals feathers, needle like, cracks, healed fractures and included lily pads and foils.

Individual pinpoints, included crystals, voids Clusters of included crystals, or voids Clouds of pinpoints

There are three types of inclusions, or processes, through which other materials can get into a crystal;

Protogenetic Inclusions: These inclusions were already present before the host mineral was formed. The host mineral grew around them. Therefore they are older than the host crystal.

Syngenetic Inclusions: Formed at the same time as the host mineral. These inclusions can be solids, liquids, or gases, or combinations of any of the three forms of matter. These inclusions are therefore the same age as the host crystal.

Epigenetic Inclusions: These inclusions were formed after the host crystal was formed. These inclusions are usually either formed by exsolution or from the recrystallization of a fracture in a host mineral. They may also be liquid, solid, or gaseous. These inclusions are therefore younger than the host crystal.

6.5 Grading the clarity of Tanzanite

Most color stone clarity grading is assumed to be with the unaided eye. The Sunlight

is used to see the clarity through/within the gemstone. But the specialized dealers

and companies of gemstones use the special equipments to minimize the human error

especially if your eyesight is below standard. The fiber light is used at TanzaniteOne

and magnification lens (10 x magnifications).

Carefully study a gemstone, observing characteristics that distract the eye or

could affect durability, transparency, brilliance and color. Mentally summarize

those observations and ask yourself in which category the gem belongs. If you

notice a minor inclusion, start your grading assessment again with that clarity

grade as a minimum.

The logic behind is to grade A/B/BL and SI/I from the cobbed Tanzanite.

A/B/BL are combined while SI/I are separated.

At this process weight is not considered, only inclusion matters. Bear in mind

here B do not only signify blue but also other colour rather than Blue. The same

rules as of Blue colour apply to other colour and named after A/B/BL and SI/I.


Table 11: Practical Example for Clarity grading

Total wt A-BL SI I D REC. COLOURED TOTAL Shaft

2095.93 73.64 84.37 1680.03 152.43 NIL 104.69 2095.16 ROM

585.38 49.33 36.23 447.56 - - 52.13 585.25 MAIN

Source: TMAA


D and Coloured already discussed on cobbing.

A-BL: These are the tanzanite and other gemstones without inclusions and

they mean A, B and BL. These go direct to colour grading without passing to

Sizing 1.

SI: These are the gemstones with Slight Inclusion. They may be A, B or BL with

inclusions. (ASI, BSI and BLSI) but these naming will be arranged on colour

grading.

I: These are the gemstones with real inclusions vividly seen. They may be A, B

or BL with vivid inclusions (AI, BI and BLI). But these colours will be

categorized during colour grading;

After that SI and I go to Sizing 1 to be graded according to their sizes from the range of

size1-14 and where;

The SI and I with sizes 1-4 (0.01 - 0.49g) are packed ready for selling.

Those from size 5-14 (0.5 - 20+g) go to Colour grading and then to sizing

2.

Generally at Clarity process, you will have three groups of Tanzanite

A, B and BL without inclusions

A, B and BL with Slight Inclusion (SI), that is ASI, BSI and BLSI and finally

A, B and BL with vivid Inclusion (I) that is AI, BI and BLI

The figure shows the clarity grading by using fiber light to identify the level of

inclusions on and within the gemstones. The figure also shows the three containers

in which those three types of Tanzanite are stored during the process.


Figure 11: Clarity grading by using fiber light

6.6 Sizing Indicator

In gemstone sizing refers to arrangement of gemstones according to their weights,

inclusions and colours. There are two types of arrangements of gemstones during

processing;

Sizing one (1) and Sizing two (2).Conversional weight is 0.2g equals to 1 carat (1ct)

Sizing one (1): This involves arrangement of gemstones from size 1-14.Those

from size 1-4 are collected and packed ready for selling and the gemstones

above size 5-14 are taken to Colour grading and then finally to Sizing two(2)

Sizing two (2): This deals with gemstones from size 5-14 and is the final

process. Though due to human error you may find the gemstones with sizes

below 5-14

Below is the table (Table 11) showing the Sizing Indicator (the range of weight and

corresponding size)


Table 12: Sizing Indicator used at TanzaniteOne

SIZE ROUGH WEIGHT(g) GRADE

1 0.01 0.09 B/BL

1 0.01 0.15 C

2 0.10 0.15 B/BL

2 0.16 0.19 C

3 0.20 0.29 B/BL/C

4 0.30 -0.49 A/B/BL/C

5 0.50 0.79 A/B/BL/C

6 0.80 0.99 A/B/BL/C

7 1.00 1.99 A/B/BL/C

8 2.00 2.99 A/B/BL/C

9 3.00 4.99 A/B/BL/C

10 5.00 6.99 A/B/BL/C

11 7.00 9.99 A/B/BL/C

12 10.00 14.99 A/B/BL/C

13 15 .00 19.99 A/B/BL/C

14 20+ A/B/BL/C

Souce: TanzaniteOne Mining Company Ltd.

6.7 Sizing One (1)

This deal in essence with the gemstones having inclusions .All gemstones with

inclusions are arranged at Sizing One with relation to their weight. Those without

inclusions are not involved at Sizing one they are direct taken to Colour grading and

Sizing two.

Remember at clarity process, the gemstones without inclusions (A, B, BL) were taken

to colour grading and then to Sizing two without passing into sizing one.SI and I

gemstones are the ones taken into Sizing one.

Table 13: Practical Example for Sizing 1

Total wt Size 1 Size 2 Size 3 Size 4 Size 5-14 Total grade Shaft

770.50 50.07 42.17 175.96 266.98 234.36 770.17 I ROM

85.49 - - - 10.65 74.81 85.46 SI CT

36.23 - - - 5.58 30.65 36.23 SI MAIN

143.77 1.71 4.12 26.62 55.84 55.40 143.69 I DELTA

21.98 - - 0.54 5.28 16.07 21.89 SI DELTA

Source: TMAA


Size1 to Size 4: The gemstones with inclusions and having weight from 0.01-

0.49g that is size 1-4 are finalized/packed for Selling. The reason is that, they

are two small for further processes like Cutting .The only further process is heat

treatment to make them more Blue violet.


Size 4 to Size 14: Those with weight from 0.5-20+g that is Size 5-14 are taken

into Colour grading then to Sizing two. These can be further treated

(cutting/polishing) therefore is better to grade them up to the final stage (Sizing

two) and the buyer will decide whether to buy rough or further treatment

(cutting/polishing).

Figure 12: Sizing One (1) process

Each beaker holds one size of gems that is size 1, 2, 3 and 4 its own beaker. While

sizes 5 up to 14 are mixed in one beaker (see the one full to the rim). At the left hand

side on the figure is the scale used for sizing (weight ranges)

6.8 Colour grading

This is the most complex process in grading Tanzanite and other gemstones. This can also be used as a loophole for tax deviations. Blue colour can be called Blue light purposely to decrease the value. Therefore the evaluators and buyers need time to cross check them though roughly to confirm the colour. But as I said the peripheral between Blue and light blue sometime not easy to mark. The same happen between Blue Light Slightly Included and Blue Slightly Included. These ambiguities were mitigated by Munsell when he introduced the concept of hue (original colour) saturation (intensity) and tone (lightness/darkness).


Saturation and Tone are used to distinguish the range of colors (range of hue) is it deep Blue, pure Blue or slightly Blue. Hue doesnt confuse because is the color that we notice immediately like red, blue, yellow, or green. Albert H. Munsel, an American painter and art instructor was the first to identify these basic qualities of a specific color - hue, saturation and tone. The GIA eventually adopted these principles to create a standardized gemstone color-grading system.

But the system has no final guidelines to base; it just gives you the blueprint of the system principles and where to start but how to finalize depends on the beauty of the beholder. Regardless of the shortcomings of GIA, it is still the only System to be referred. The figure 9, 10 and 11 will help us to build the concept of saturation and tone before we go into practical example.

Figure 13: Gemstone Hue Chart

Saturation is the intensity of the hue present in a color sensation. Colors of low

saturation are sometimes called weak, grayish or brownish while those of high

saturation are said to be highly saturated, strong or vivid.

Figure 14: Gemstones Saturation chart


Tone indicates the lightness or darkness of a color sensation. The scale ranges from 0

for pure black to 10 for pure white. Black and white and the grays between them are

called neutral colors. They have no hue. Colors that have a hue are called chromatic

colors. Colors that do not have a hue are known as achromatic. The value scale

applies to chromatic as well as to neutral colors. GIA uses 7 of those steps (Tones 2

thru 8) for grading tone in transparent colored gemstones.

Figure 15: Gemstone Tone chart

NOTE: From the above concepts of Hue, Saturation and Tone, one can still get stuck

to distinguish between Saturation and Tone. Am I wrong? And still no quantitative

techniques to mitigate the confusion.

6.8.1 GIA Colour grading steps

Judge hue and saturation by identifying the Key Colors which are direct seen. We do

that by face up stone and find the Key colors - the colors under the crown facets which

show the best representation of color in the stone. The fiber light is used to assist to

identify the colour satisfactorily. We do not consider washed out, windowed, or areas

of extinction;

Windowing refers to the washed out area in the center of a stone

generally seen through the table. A stone with a large washed out area is

said to have a large window.

Extinction refers to the areas of darkness visible through the crown.

These areas appear gray or black.

Brilliance is a measure of the light which enters the stone and reflects

back to our eye. It is seen as the bright areas or flashes within the stone.

You may see these steps; they just explain how to start but dont comment how to arrive

to the final judgment. The Crown, Window /table, girdle these can be seen after cut but

for rough gemstone not ease to know the crown and window sides. These are

shortcomings of GIA.


6.8.2 TanzaniteOne Colour grading steps

Tanzanite Gemstones are arranged according to the standard colour. People do

confuse Colour grading with clarity grading .During clarity grading, the criteria is to

look on the inclusions only, grade those without inclusions and those with inclusions

regardless of their colour. While Colour grade is based on colour, weight and

inclusion.

Here the standard colour has already implemented. Blue colour is a Key Colour in

grading all gemstones available at TanzaniteOne. Tanzanite is predominantly Blue and

brown. When heated it turns Blue-Violet permanently. Tsavorite is greenish and

Coloured gemstones are pale blue and pale brown. Tsavorite is separated but the rest

are graded based on blue colour. There are A, B, BL, BSI, BLSI, BI and BLI types of

colour. Those gemstones which are not blue are named after blue colour as I said

before. Suppose the gemstone is brown or yellow it will be named as Blue, B and if

slightly brown/yellow it will be named Blue light, BL etc

For beginners, the Master stones or Master colours are used to differentiate the

colour until the grader become experienced with those colours and start doing grading

in his/her own.

Table 14: Practical example for Tanzanite Colour grading at TanzaniteOne

Total wt A B BL COLOUR YELLOW WASTE TOTAL Shaft

470.12 - 88.87 362.67 18.51 - - 470.05 CT

119.72 - 20.68 86.79 12.39 - - 119.86 DELTA

Source: TMAA

Master colours referred for tanzanite

COLOURED BL B A


A: Is the exceptional colour, deep Blue without inclusions. Very rare to get it.

B: Blue or Brown or any visible colour

BL: Blue light or Brown light or any light colour

Colour: Pale Blue, Brown or any pale colour.

The same process as for Clarity grading is used and also fiber light is used (refer

figure)


6.9 Sizing two (2)

The intention of this section is to grade the gems according to their weight, colour and

inclusions. We already have colour grading; the last stage is to arrange those gems

with reference to their weight and colour. In essence Sizing two (2) deal with gems

from Size 5 onward. Therefore expect to get more gems at Sizing two with Size 5 and

higher. But due to human error, the gems with weight less than Size 5 are found

taken to Sizing two stage. Thats why sometime size 1, 2, 3 and 4 appear at Sizing two

(2) stages instead of being collected at Sizing One.

Table 15: Practical Example for Sizing two (2) Total

wt

Grade SIZE

2

SIZE

3

SIZE

4

SIZE

5

SIZE

6

SIZE

7

SIZE

8

SIZE

9

SIZE

10

Total

12.79 B - - 1.32 1.61 1.89 3.20 - 4.81 - 12.83

270.18 BL 1.79 17.15 86.30 90.50 27.70 37.80 8.92 - - 270.16

16.80 BSI - - - 5.12 2.69 8.44 - - - 16.75

124.21 BLSI - - - 78.67 20.51 25.07 - - - 124.25

77.53 BI - - - 43.84 14.80 18.90 - - - 77.54

400.78 BLI - - - 343.82 40.70 16.31 - - - 400.83

31.28 B - - 0.4 1.91 6.06 9.86 - 7.10 5.94 31.27

164.69 BL - - 28.58 41.80 14.95 53.27 6.77 9.26 5.77 164.61

6.82 BSI - - - 2.95 2.45 1.30 - - - 6.70

40.05 BLSI - - - 17.61 12.33 8.00 2.01 - - 39.95

18.61 BI - - - 12.11 0.92 5.58 - - - 18.61

66.74 BLI - - - 58.04 5.07 3.61 - - - 66.72

Source: TMAA

The above can be also presented as following;

Grade Weight(g) Grade Weight(g)

4B 1.72 5B(SI) 8.07

5B 3.52 6B(SI) 5.14

6B 7.95 7B(SI) 9.74

7B 13.06 5BL(SI) 96.28

9B 11.91 6BL(SI) 32.84

2BL 1.79 7BL(SI) 33.07

3BL 17.15 8BL(SI) 2.01

4BL 114.88 5B(I) 55.95

5BL 132.3 6B(I) 15.72

6BL 42.65 7B(I) 24.48

7BL 91.07 5B(LI) 401.86

8BL 15.69 6B(LI) 45.77

9BL 9.26 7B(LI) 19.92

10BL 5.77


7.0 GEMSTONE TREATMENTS, ENHANCEMENTS, AND CARE

As critical as good cutting and polishing is, treatments have become an integral part of the modern gemstone industry. While these treatments are taken as commonplace within the industry, the general public's awareness has been much lower.

Enhancements: Virtually all gem tanzanite of a blue violet color has been heat-treated to enhance the color. In the rough state most Tanzanite is predominantly brown and blue light. Heating at 500 to 600 degrees centigrade causes this color to change to blue. This is a permanent and stable change.

Is The Use Of Treatments Globally Accepted ?YES, the majority of gemstones traded internationally have undergone some form of treatment with close to 99% of the more popular gem types being treated. All permanent techniques are universally accepted. Are All The Treatments Used Permanent? Except for Emeralds that are treated with colorless oil or polymers, most gemstone treatments are permanently stable with normal wear.

Care of Tanzanite Gemstones. Due to Tanzanite's relative softness, it should be treated with respect. It is not a gem

that should break easily but due to its relatively low score on the Mohs Scale (6) it can scratch more easily than other gems like Ruby. To clean it does not use an ultrasonic cleaner or steam cleaner often found in jewelers. The best method is simply to use a toothbrush and warm, soapy water. Similarly, when setting your Tanzanite gem your jeweler should realize that he should be careful and not use undue levels of heat. Table 15 shows the treatment methods of different gemstones.

PUBLIC POINTS OF

INTEREST TO BE

ADDRESSED

Few people who know that

Tanzanite is heated to get Blue

violet colour. This treatment

increases the value of tanzanite

like Cuts of tanzanite did.

IF THAT IS THE CASE

The Government has posed a ban

of cutting the Tanzanite abroad.

What about the heat treatment?

TUCSON TANZANITE

PROTOCOL

The purpose of the protocol is to

safeguard the Tanzanite from

dirty hands!! Do the protocol

under control of all shareholders

who signed it or is only now

under control of the

TanzaniteOne who only care

about the Sales regardless of who

buy the tanzanite?

By

Compiler


8.0 GEMSTONES CUT AND POLISH

Second Compilation will include this process of Tanzanite cutting techniques in details. For now just have some partial hints of cutting techniques.

The process of cutting and polishing gems is called gemcutting or lapidary, while a person who cuts and polishes gems is called a gemcutter or a lapidary. Gemstone material that has not been extensively cut and polished is referred to generally as rough. All gems are cut and polished by progressive abrasion using finer and finer grits of harder substances. Diamond, the hardest naturally occurring substance is used as an abrasive to cut and polish a wide variety of materials, including diamond itself.

8.1 Cutting Techniques

Several common techniques are used in lapidary work: Sawing, grinding, sanding, lapping, polishing, drilling and tumbling.

Sawing: A thin circular blade usually composed of steel, copper, or a phosphor

bronze alloy impregnated along the outer edge with diamond grit and rotating at

several thousand surface feet per minute literally scratches its way through a

gemstone.

Grinding: with silicon carbide wheels or diamond-impregnated wheels,

gemstone is shaped to a desired rough form, called a preform.

Sanding is similar to grinding but uses finer abrasives. Its purpose is to remove

deep scratches left by coarser abrasives during grinding.

Lapping is very similar to grinding and sanding, except that it is performed on

one side of a rotating or vibrating flat disk known as a lap, and it is used

especially to create flat surfaces on a stone (as in faceting).

Polishing: After a gemstone is sawed and ground to the desired shape and

sanded to remove rough marks left by coarser grits, it is usually polished to a

mirror-like finish to aid light reflection from the surface of the stone or

refraction through the stone, in the case of transparent materials.

Tumbling: Large quantities of roughly shaped stones are often tumbled, i.e.,

turned at a slow speed in a rotating barrel with abrasives and water for

extended periods of days or weeks. By tumbling with progressively finer grades

of abrasive and washing carefully between grades, the stones are gradually

smoothed and polished.


Cabochons: One of the simplest lapidary forms is the cabochon, a stone that is

smoothly rounded and polished on top, relatively flattish, and either flat or

slightly rounded on the bottom. This form of cutting is often used for opaque or

translucent stones, but is also frequently used for transparent materials that

contain too many inclusions to yield a good faceted stone. Coloration and

patterning provide the major interest in such stones.

Faceted Stones: Faceting is most often done on transparent stones. Flat facets

are cut and polished over the entire surface of the stone, usually in a highly

symmetrical pattern.

Inlays: In an inlay, a gemstone is cut to fit and glued into a hollow recess in

another material (metal, wood, or other stones) and then the top ground and

polished flush with the surrounding material.

Intarsias and Mosaics: In both intarsia and mosaic work, small bits of different

colored stones are fit together and the top cut and polished to present a picture

or other interesting pattern

Sculpture: Gemstones can be carved, like other materials, into almost any

form, limited only by the talents of the sculptor. Carving is accomplished with a

variety of diamond-impregnated steel bits.

9.0APPENDICES

Appendix 1: Birthstones & Anniversary Gemstones

Month Gemstone

Jan Garnet

Feb Amethyst

Mar Aquamarine

Apri Diamond

May Emerald

June Alexandrite

July Ruby

Aug Peridot

Sept Sapphire

Oct Opal, Pink Tourmaline

Nov Topaz

Dec Tanzanite


Appendix 2: Anniversary Gemstones

Year Gemstone

1st Remembrance or Gold

2nd Remembrance or Garnet

3rd Remembrance or Pearl

4th Remembrance or Blue Topaz

5th Remembrance or Sapphire

6th Remembrance or Amethyst

7th Remembrance or Onyx

8th Remembrance or Tourmaline

9th Remembrance or Lapis Lazuli

10th Remembrance or Diamond

11th Remembrance or Turquoise

12th Agate or Jade

13th Citrine or Moonstone

14th Opal or Moss Agate

15th Ruby or Rock Crystal

16th Peridot or Topaz

17th Amethyst

18th Garnet or Cats Eye Chrysoberyl

19th Aquamarine, Rose Quartz, or Rhodochrosite

20th Emerald or Jade

21st Iolite

22nd Spinel

23rd Imperial Topaz

24th Tanzanite

25th Silver Jubilee


30th Pearl Jubilee

35th Emerald, Coral, or Jade

40th Ruby

45th Sapphire

50th Gold Jubilee

55th Emerald or Alexandrite

60th Diamond Jubilee

65th Blue Spinel

70th Sapphire Jubilee

75th Diamond Jubilee

80th Ruby Jubilee

Appendix 3: Weekday

Sunday ~ Golden Topaz, Sunstone, Amber

Monday ~ Pearl, Moonstone, Rock Crystal

Tuesday ~ Ruby, Emerald, Star Sapphire, Garnet

Wednesday ~ Amethyst, Lodestone, Star Ruby, Turquoise, Sapphire, Lapis Lazuli

Thursday ~ Sapphire, Carnelian, Amethyst, Cat's Eye (Chrysoberyl)

Friday ~ Emerald, Cat's Eye (Chrysoberyl), Alexandrite, Agate, Malachite

Saturday ~ Diamond, Turquoise, Labradorite


10: REFERENCES

1. UNDP, 1998 World Report on Gemstones Mining.

2. TMAA Database. http://www.tmaa.go.tz

3. How are gems cut and polished. http://www.tradeshop.com/gems/howcut.html

4. Conrad Mtui, TMAA TanzaniteOne Analytical Report ,2011

5. Physical and optical properties of Minerals and gemstones. http://www.rocksinmyheadtoo.com/PhysOpti.htm

6. The gemstones cutting process.

http://www.gemstoneartist.com/Process.asp

7. Understand tanzanite GIA colour grades. http://www.lapigems.com/tanzanite.asp

8. Tanzanite unique properties. http://www.etanzanite.com/tanzanite_pictures.htm

tanzanite processing steps manual by eng gilayshamika

Documents

tanzanite processing

gemstones colour

unique features of tanzanite

cs of gemstones

optical properties

colour grading

physical properties

rom sort recovery