tecto silicates
DESCRIPTION
Tectosillicates reportTRANSCRIPT
TECTOSILICATES
Tectosilicates (framework silicates)
•Name came from the Greek tectron, meaning “builder”.
•The Tectosilicate structure is a three-dimensional network of silica tetrahedra, with each tetrahedral unit sharing all of its four oxygen atoms.
•The largest single group of silicates, and include several rock-forming minerals.
TECTOSILICATE GROUPS
SiO Group
•The SiO2 structure is electrically neutral – it does not require additional cation or anion species.
•SiO2 is quartz in its simplest form.
2
QUARTZ
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHIN
G FEATUR
ES
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACI
TYSTREAK
SiO2
Hexagonal
Colorless or white
7 2.65 vitreous conchoidal brittle
Colorless or white
Distinguished from calcite by its high hardness
Gemstones, manufacture of glass and silica brick, porcelain and sandpaper
QUARTZ
TRIDYMITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING
FEATURESUSES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACI
TYSTREAK
SiO2
Monoclinic/ Orthorhombic-hexagonal
Colorless or white
7 2.26
vitreous
conchoidal
brittle
Colorless or white
Crystalline outline and refractive index
Ceramics
TRIDYMITE
CRYSTALOBALITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHIN
G FEATUR
ES
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACI
TYSTREAK
SiO2
Tetragonal-isometric
Colorless 7 2.32 vitreous conchoid
al brittleColorless or white
Exhibits double refraction, sometimes fluorescent white cream
Ceramics
CRYSTALOBALITE
OPAL
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHIN
G FEATUR
ES
USES
COLOR
HARDNESS
SPECIFIC GRAVITY
LUSTER FRACTURETENACITY
STREAK
SiO2
nH2
O
Amorphous
Colorless or white, sometimes it have pale colors because of impurities
5-6
2.25
Vitreous
conchoidal
brittle White
Lesser hardness and specific gravity and by presence of water
Gem
OPAL
JASPER
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHIN
G FEATUR
ES
USES
COLOR
HARDNESS
SPECIFIC GRAVITY
LUSTER FRACTURECLEAVAGE
STREAK
SiO2
Hexagonal/trigonal
Red, yellow brown and numerous others
7 2.7 Vitreous
conchoidal
none White
Brick-red to brownish-red contains hematite ; clay to yellowish-white or grey; goethite produces brown or yellow.
Jewelry and ornamentation
JASPER
CHALCEDONY
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHIN
G FEATUR
ES
USES
COLOR
HARDNESS
SPECIFIC GRAVITY
LUSTER FRACTURECLEAVAGE
STREAK
SiO2
Hexagonal/trigonal
white 7 2.7 Waxy to dull
conchoidal
none White Relatively
porous ceramics
CHALCEDONY
AGATE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHIN
G FEATUR
ES
USES
COLOR
HARDNESS
SPECIFIC GRAVITY
LUSTER FRACTURETENACITY
STREAK
SiO2Amorphous
Colorless or white, sometimes it have pale colors because of impurities
5-6
2.25
Vitreous
conchoidal
brittle White
Lesser hardness and specific gravity and by presence of water
Gem
AGATE
FELDSPAR GROUP
•A group of aluminosilicate minerals that contain calcium, sodium or potassium.
•The most common minerals on earth’s crust.
•Feldspars are the major component of most igneous rocks.
•There are two groups of feldspars: the ALKALI FELDSPARS and PLAGIOCLASE FELDSPARS.
ALKALI FELDSPARS
•The alkali feldspar group are those feldspar minerals rich in the alkali elements, potassium and sodium.
•Potassium and sodium feldspars are not perfectly miscible in the melt at low temperatures, intermediate compositions of the alkali feldspars therefore occur only in higher temperatures environments
MICROLINE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
KAISi3O8
Triclinic
White to pale yellow
62.54 – 2.57
Vitreous
conchoidal
brittle white
Distinguished from orthoclase by the microcline (“tartan”) twinning
Manufacture of porcelain
MICROLINE
ORTHOCLASE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
KAISi3O8
Monoclinic
White to gray
6 2.57Vitreous, pearly
conchoidal
brittle white
Right angle cleavage and insoluble in acids
Manufacture of porcelain, sometimes in gemstones
ORTHOCLASE
SANIDINE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
(K,Na)AISi3
O8
Monoclinic
colorless 6
2.56 – 2.62
Vitreous, pearly
conchoidal
brittle white
Optic orientation differs from orthoclase and show different types of twinning compared to plagioclase
Ceramics
SANIDINE
ANORTHOCLASE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
(Na,K)AlSi3O
8
triclinic
Colorless to white
6-6.5
2.6 vitreousConchoidal to uneven
brittle white Oblique
cleavageornaments
ANORTHOCLASE
PLAGIOCLASE FELDSPARS
•The series ranges from albite to anorthite endmembers (with respective compositions NaAlSi3O8 to CaAl2Si2O8), where sodium andcalcium atoms can substitute for each other in the mineral's crystal lattice structure.
•Plagioclase in hand samples is often identified by its polysynthetic twinning or 'record-groove' effect.
PLAGIOCLASE FELDSPARS
•The composition of a plagioclase feldspar is typically denoted by its overall fraction of anorthite (%An) or albite (%Ab), and readily determined by measuring the plagioclase crystal's refractive index in crushed grain mounts, or its extinction angle( an optical characteristic and varies with the albite fraction (%Ab)) in thin section under a polarizing microscope.
ALBITE (%An: 0-10, %Ab: 100-90)
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
NaAISi3O8
Triclinic
Colorless, white or gray
6 2.62Vitreous, pearly
subconchoidal
brittle white
Twin striations, insoluble in HCl
Ceramics
ALBITE
OLIGOCLASE (%An: 10-30, %Ab: 90-70)
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
(Ca,Na)(Al,Si)4O8
triclinic
Grey, white 6 2.5 vitreous
Conchoidal to uneven
brittle white
Usual habit is massive or granular, does form tabular crystals, commonly twinned
OLIGOCLASE
ANDESINE (%An: 30-50, %Ab: 70-50)
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURECLEAVAGE
STREAK
(Ca,Na)(Al,Si)4O8
triclinic
Grey, white
6-6.5
2.7Subvitreous to pearly
Conchoidal to uneven
perfect white
Exhibits multiple twinning
ANDESINE
LABRADORITE (%An: 50-70, %Ab:50-30)
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURECLEAVAGE
STREAK
(Ca,Na)(Al,Si)4O8
triclinic
Blue, grey, white
6-6.5
2.7 vitreous
Uneven to conchoidal
perfect white
Play of iridescent colors
gemstone
LABRADORITE
ANORTHITE (%An: 90-100, %Ab: 10-0)
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATUR
ES
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
CaAl2
Si2O
8
Triclinic
colorless 6 2.76 Vitreou
sconchoidal
brittle white
Twin Striations, decomposed in HCl
Ceramics
ANORTHITE
FELDSPATHOID GROUP
Feldspar-like minerals that are deficient in silica content. These are relatively rare and are important in the classification of igneous rocks.
LEUCITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATUR
ES
USES
COLOR
HARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
KAlSi2O6
Tetragonal
White to gray
5.5-6
2.47 Vitreous, dull
conchoidal
brittle white
Infusible, trapezohedral form
Fertilizer, artificial alum
LEUCITE
NEPHELINE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
(Na,K)AlSiO4
Hexagonal
Colorless to yellowish
5.5-6
2.60- 2.65
Vitreous, greasy
subconchoidal
brittle white Gelatinizin
g in acidGlass industry
NEPHELINE
SODALITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
Na8Al6Si6
O24Cl
2
Isometric Blue 5.5-
6
2.15- 2.30
Vitreous uneven britt
le white
Soluble in HCl, produces silica jelly when evaporated and its blue color
Ornament
SODALITE
LAZURITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
(Na,Ca)8
Al6Si
6O24(S,SO)4
Isometric
Deep Azure-Blue
5-5.5
2.40- 2.45
Vitreous, greasy
uneven brittle blue
Blue color and presence of associated pyrite
Lapis Lazuli-high prized ornament stone
LAZURITE
PETALITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
Li(AlSi4O1
0)
Monoclinic
Colorless to gray
6-6.5 2.4
Vitreous, pearly
uneven brittle white Platy habit,
InsolubleOre of lithium
PETALITE
SCAPOLITE SERIES
The scapolites (Gr. asairos, rod, stone) are a group of rock-forming silicate minerals composed of aluminium, calcium, and sodium silicate with chlorine, carbonate and sulfate. The two endmembers are meionite (Ca4Al6Si6O24CO3) and marialite (Na4Al3Si9O24Cl).
MARIALITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
Na4(Al3Si
9O24)Cl
Tetragonal
White to gray
5-62.55- 2.74
Vitreous
conchoidal
brittle white
Fibrous appearance on the cleavage surface
Gemstone
MARIALITE
MEIONITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
Ca4(Al6Si
9O24)(CO3)
Tetragonal
White to gray
5-62.55- 2.74
Vitreous, dull
conchoidal
brittle white
Fibrous appearance on the cleavage surface
Gemstone
MEIONITE
ANALCIME
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
NaAlSi2O6
H2O
Isometric
White or colorless
5-5.5 2.27 Vitreo
usconchoidal
brittle white
Gives water in the closed tube, free growing crystals
For building materials
ANALCIME
ZEOLITE SERIES
These are hydrous Ca and Na tectosilicates, which have Al present in both tetrahedral and octahedral sites.
The name is derived from the fact that when you fuse ground up mineral, it swells. Zeo means boil and lite means stone (from the Greek).
NATROLITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
Na2Al2Si3O10-2H2
O
Orthorhombic
White or colorless
5-5.5 2.25 Vitreo
us
Uneven-conchoidal
brittle white
Gives water in the closed tube, and gelatinizes upon evaporation
Ornament
NATROLITE
CHABAZITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
Ca2Al2Si4O12 - 6H2
O
Hexagonal
White or colorless
4-52.05-2.15
Vitreous uneven britt
le white Rhombohedral crystals Ornament
CHABAZITE
HEULANDITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
(Ca,Na)2-
3Al3(Al,Si)2Si13
O36 · 12H2
O
Monoclinic
White or colorless, yellow, or red
3.5-4
2.18-2.2
Vitreous, pearly
conchoidal
brittle white
Gives water in the closed tube, one direction of perfect cleavage
Ornament
HEULANDITE
STILBITE
CHEMICAL COMPOSITION
CRYSTAL SYSTEM
PHYSICAL PROPERTIES
DISTINGUISHING FEATURE
S
USES
COLORHARDNESS
SPECIFIC
GRAVITY
LUSTER FRACTURETENACITY
STREAK
CaAl2Si7
O18 · 7(H2
O)
Monoclinic
White
3.5-4
2.1-2.2
Vitreous, pearly
uneven brittle
colorless
Pearly luster on cleavage part, sheaflike group of crystals
Ornament
STILBITE