Minerals

Ch. 9

9.1 What is a mineral?

• Minerals• Inorganic• A. Kinds of minerals• B. Silicate minerals• Nonsilicated minerals• C. Crystalline structure• The crystalline structure of silicate minerals• Isoloated tetrahedral silicates and rign silicates• Single-chain silicates, double-chain silicates,

sheet silicates, and framework silicates

Mineral

• Ex. Ruby, gold nugget, salt

• Definition :A natural, inorganic, crystalline solid

• Natural means not man made

• Inorganic means not made up of any living pieces dead or alive

• Crystalline solid means crystal form.

How to tell if something is a mineral.

• 4 basic questions – if yes to all 4 it is a mineral.

1. Is it inorganic? – no carbon

2. Occur naturally? – not man made

3. Solid in crystalline form?

4. Definite chemical composition – element or compound

A. Kinds of Minerals

• There are over 3,000 different minerals.

• Fewer than 20 are common

• Common minerals are rock forming minerals. They form rocks on the earths crust.

• 90% of earth’s crust made up of 10 common minerals

10 most common rock minerals

• Quartz• Orthoclase• Plagioclase• Muscovite• Biotite• Calcite• Dolomite• Halite• Gypsum• ferromagnesian

2 groups of minerals

• 1. Silicate

• 2. Nonsilicate

Silicate minerals

• 96 % of earths crust is made of silicate minerals.• Feldspar and quartz make up 50% of crust• Silicate minerals – contain atoms of silicon(Si) and

Oxygen (O).• Quartz – only silicon and oxygen• Feldspars – most common, types depend on metal

mixed with Si and O2• Orthoclase – K• Plagioclase – Na or calcium or both• Ferromagnesian – Fe and Mg • (olivines, pyroxenes, amphiboles, biotite)

Nonsilicate Minerals

• 4% of crust• Do not contain silicon• 6 groups• 1. carbonates – contains carbonate group dolomite and

calcite• 2. Halides – chlorine or fluorine w/Na, K, Ca halite• fluorite• 3. Native elements – uncombined Ag, Cu• 4. Oxides – O2 corundum, hematite• 5. Sulfates – sulfate gypsum, anhydrite• 6. sulfides – sulfur galena, pyrite

Crystalline structure

• Natural solid with a geometric pattern• Use of xrays to identify

• A. Isoloated tetrahedral silicates and ring silicates

• B. Single-chain silicates, double-chain silicates, sheet silicates, and framework silicates

The crystalline structure of silicate minerals

• Silicon-oxygen tetrahedron – basic building blocks of 4 O2 in a pyramid and 1 silicon

Isolated tetrahedral silicates and ring silicates

• The tetrahedral bonds with other elements

• Rings are formed when tetrahedral bind in 3’s

Single-chain silicates, double-chain silicates, sheet silicates, and

framework silicates• Single chain• Tetrahedron bonded to 2 others by shared O2• Pyroxenes• 2 single chains bond together• Amphiboles• Sheet – sharing 3 O2 with other tetra, 4th with K

or Al • Micas• Framework - tetra bonds with 4 other tetra• quartz

9.2 Identifying Minerals• A. Characteristics of minerals• 1. color• 2. Luster• 3. Streak• 4. Cleavage and fracture• 5. Hardness• 6. Crystal shape• 7. Density• B. special properties of minerals• 1. magnetism• 2. fluorescence and phosphorescence• 3. double refraction• 4. radioactivity

A. Characteristics of minerals

• 1. color

• 2. Luster

• 3. Streak

• 4. Cleavage and fracture

• 5. Hardness

• 6. Crystal shape

• 7. Density

1. color

• Sulfur – bright yellow• Azurite – deep blue• Cinnabar – red• Serpentine – green

• little mineral can be a lot of color• Ruby• Sapphire• Quartz• Iron pyrite changes gold to yellow with weathering

2. Luster

• Light reflected from the surface

• 1. Metallic luster - shiny

• 2. Nonmetalic luster – glassy, waxy, pearly

• Dull (earthy) luster – lacks shine

3. Streak

• Mineral in powder form

• Draw (rub) on tile

• Dark is usually metal

• Nonmetals – colorless or light

4. Cleavage and fracture

• Ability to cut along flat surface• Based on weak bonds

• Fracture – break into irregular pieces• Types:• 1. Uneven or irregular - rough• 2. Splintery or fibrous – broken wood• 3. Conchoidal - curved

5. Hardness

• Ability to Resist scratching

• Mohs hardness scale• 1-10 • 1 soft• 10 hardest

• Scratch test• Strength of bonds

Mohs hardness scale• HardnessMineralAssociations and Uses• 1TalcTalcum powder.• 2GypsumPlaster of paris. Gypsum is formed when seawater evaporates

from the Earth’s surface.• 3CalciteLimestone and most shells contain calcite.• 4FluoriteFluorine in fluorite prevents tooth decay.• 5ApatiteWhen you are hungry you have a big "appetite".• 6OrthoclaseOrthoclase is a feldspar, and in German, "feld" means "field".• 7Quartz • 8TopazThe November birthstone. Emerald and aquamarine are varieties of

beryl with a hardness of 8.• 9CorundumSapphire and ruby are varieties of corundum. Twice as hard as

topaz.• 10DiamondUsed in jewelry and cutting tools. Four times as hard as

corundum.

Hardness of some other items:

• 2.5Fingernail• 2.5–3Gold, Silver• 3Copper penny• 4-4.5Platinum• 4-5Iron• 5.5Knife blade• 6-7Glass• 6.5Iron pyrite• 7+Hardened steel file

6. Crystal shape

• Minerals always combine with the same geometric pattern

• 1. isometric or cubic system• 2. triclinic system• 3. Hexagonal system• 4. orthorhombic system• 5. monoclinic system• 6. tetragonal system

7. Density

• D = m/v

• Will feel heavier – lead, gold

B. special properties of minerals

• 1. magnetism

• 2. fluorescence and phosphorescence

• 3. double refraction

• 4. radioactivity

1. magnetism

• Magnetic will attract iron

• Ex. Magnetite is most common

• Lodestone is a form of magnetite

• Acts like a bar magnet with poles (N&S)

• Used as compass by early navigation

2. fluorescence and phosphorescence

• Ability to glow under UV light

• Ex. Calcite white appears >red under UV light

• Absorbs UV and produces visible light

• Willemite light brown > green under UV

• Phos. – glows after UV light off

3. double refraction

• Refraction – light rays bending as pass through crystals of calcite produces double image

4. radioactivity

• Unstable e- arrangement or proton and neutrons in nucleus

• Ex. U or Ra

• U – pitchlende, carnotite, uraninite, autotite

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