Minerals
Ch. 9
9.1 What is a mineral?
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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.
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4 basic questions – if yes to all 4 it is a
mineral.
Is it inorganic? – no carbon
Occur naturally? – not man made
Solid in crystalline form?
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
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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
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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
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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
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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
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1. color
2. Luster
3. Streak
4. Cleavage and fracture
5. Hardness
6. Crystal shape
7. Density
1. color
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Sulfur – bright yellow
Azurite – deep blue
Cinnabar – red
Serpentine – green
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little mineral can be a lot of color
Ruby
Sapphire
Quartz
Iron pyrite changes gold to yellow with weathering
2. Luster
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Light reflected from the surface
1. Metallic luster - shiny
2. Nonmetalic luster – glassy, waxy, pearly
Dull (earthy) luster – lacks shine
3. Streak
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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
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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
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Mohs hardness scale
1-10
1 soft
10 hardest
• Scratch test
• Strength of bonds
Mohs hardness scale
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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:
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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
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1. magnetism
2. fluorescence and phosphorescence
3. double refraction
4. radioactivity
1. magnetism
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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
Shelby Gem Stone Factory