mineral. composition of the crust minerals are the chemicals that make up the earth...

Mineral

Composition of the Crust

Minerals are the Chemicals that make up the Earth

• NATURALLY-OCCURRING

• INORGANIC

• CHEMICAL COMPOUNDS

• ABOUT 3000 KNOWN

• 200 COMMON

• 20 ROCK-FORMING

Atomic Bonding 1. IONS

Atomic Bonding2. ELECTRICAL NEUTRALITY• (+) and (-) Cancel Out

3. BONDING (SATISFY 1 & 2)• Ionic (NaCl) • Covalent (O2) • Metallic (Cu, Al, Fe) • Hydrogen (in water)

Ionic and Covalent Bonding

Metallic Bonding

Hydrogen Bonding

Summary of Bonding

• Ionic bonding holds rocks and minerals together

• Covalent bonding holds people and other organisms together

• Metallic bonding holds civilization together

• Hydrogen bonding gives water its heat-retaining and solvent properties

4. Lattices• Atoms in crystals form a repeating pattern

called a Lattice

5. Radicals• Many minerals contain groups of atoms that

behave as single units

NAMING MINERALS COLOR• Glauconite (Greek: Glaucos = Blue-green) OTHER PROPERTIES, USES• Magnetite COMPONENTS• Chromite PLACES• Muscovite (Moscow) PEOPLE• Biotite

CHEMICALS (AND MINERALS) ARE

CLASSIFIED BY THEIR ANIONS

For Example: Iron Compounds Have Little in Common

• Fe: Gray, Metallic

• FeCl2: Light Green, Water Soluble

• FeSO4: Light Green, Water Soluble

• FeCO3: Brown, Fizzes in Acid

• FeS2: Dense, Brittle, Metallic, Cubic Crystals

On the Other Hand, Sulfides have Many Properties in Common

• FeS2

• CuFeS2

• PbS

• ZnS2

All are Dense, Brittle, Metallic, have Cubic Crystals

IdentifyingMinerals

IDENTIFYING MINERALS

COLOR -Sometimes Distinctive

• Often Unreliable

• Affected By:– Chemical Impurities – Surface Coating – Grain Size – Weathering

IDENTIFYING MINERALS (Continued)

HARDNESS • Resistance to Scratching • Directly related to relative strength of

atomic bonds • Scratch Test (Mohs) • Indentation Test (Knoop) Common Errors due to:• Weathering, ‘Chalk' marks • Breaking vs. Scratching

Mohs vs. Knoop Scales 1. Talc: very small 2. Gypsum, Fingernail: 30 3. Calcite, Penny: 135 4. Fluorite: 163 5. Apatite: 430 6. Feldspar, Glass: 560 7. Quartz: 820 8. Topaz: 1340 9. Corundum: 2100 10. Diamond: 7000


DENSITY

• Directly related to masses of component atoms and their spacing

• Usually very consistent

DENSITY - gm/cm3

(weight relative to water )• Air: 0.001

Wood - Balsa: 0.1, Pine: 0.5, Oak: 0.6-0.9Gasoline: 0.7, Motor Oil: 0.9Ice: 0.92Water: 1.00Sugar: 1.59Halite: 2.18Quartz: 2.65Most Major Minerals: 2.6-3.0Aluminum: 2.7

DENSITY• Pyrite, Hematite, Magnetite: 5.0

Galena: 7.5Iron: 7.9Copper: 9Lead: 11.4Mercury: 13.6Uranium: 19Gold: 19.3Platinum: 21.4Iridium: 22.4 (densest material on Earth)


LUSTER

• Metallic or Nonmetallic is the most important distinction.

• Resinous, waxy, silky, etc. are self-explanatory.

• Vitreous is often used for glassy luster.


CLEAVAGE • Tendency to split along smooth planes

between atoms in crystal • Thus directly related to atomic structure • Related to Crystal Form • Every cleavage face is a possible crystal face • Not every crystal face is a cleavage face.

Quartz commonly forms crystals but lacks cleavage.


CRYSTAL FORM

• Takes Luck & Practice

• Well-formed crystals are uncommon

• Crystal Classification is somewhat subtle

FRACTURE


GEOLOGIC SETTING • Some minerals occur in all geologic settings:

quartz, feldspar, pyrite • Some minerals occur mostly in sedimentary

settings: calcite, dolomite • Some minerals occur mostly in igneous

settings: olivine • Some minerals occur mostly in metamorphic

settings: garnet, kyanite


SPECIAL PROPERTIES

• Taste, Magnetism, Etc.

EXPERIENCE AND READING

PROFESSIONAL METHODS

• Chemical Analysis

• X-Ray Studies

• Thin Section

Diffraction

MAJOR MINERAL SUITES

ELEMENTS

Metallic:Au, Ag, Cu

• Not Al, Pb, Zn, Fe, etc.

Nonmetallic: C - Diamond, Graphite

• Sulfur


SULFIDES: Dense, Usually MetallicMany Major Ores

• Pyrite FeS2

• Chalcopyrite CuFeS2

• Galena PbS

• Sphalerite ZnS2

• Molybdenite MoS2


HALIDES: Usually Soft, Often Soluble

• Halite NaCl

• Fluorite CaF2

SULFATES: Soft, Light Color

• Gypsum CaSO4

• Barite BaSO4


OXIDES: Often Variable, Some Ores

• Hematite Fe2O3

• Bauxite Al(OH) 3 (a hydroxide)

• Corundum Al2O3 (Ruby, Sapphire)

CARBONATES: Fizz in Acid, Give off CO2

• Calcite CaCO3

• Dolomite CaMg (CO3)2

MOST IMPORTANT MINERAL SUITE:

The Silicate Minerals

• Si + O = 75% of Crust

• Silicates make up 95% + of all Rocks

• SiO4: -4 charge

• Link Corner-To-Corner by Sharing Oxygen atoms

Nesosilicates - Isolated Tetrahedra

Representatives:•Garnet •Kyanite •Olivine

Sorosilicates - Paired Tetrahedra

Epidote is the most common example

Cyclosilicates - Rings

•Beryl (Emerald) •Tourmaline

Inosilicates - Chains Single Chains (Pyroxenes)

Inosilicates - Chains Double Chains (Amphiboles)

Phyllosilicates - Sheets

Phyllosilicates - Sheets

Si2O5 sheets with layers of Mg(OH)2 or Al(OH)3

• Micas

• Clay minerals

• Talc

• Serpentine (asbestos) minerals

Tectosilicates - Three-Dimensional Networks

• Quartz Feldspars

Unit Cells All repeating patterns can be described in terms

of repeating boxes

The problem in Crystallography is to reason from the outward shape to the unit cell

Which Shape Makes Each Stack?

Stacking Cubes

Some shapes that result from stacking cubes

Symmetry – the rules behind the shapes

The Crystal Classes

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