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 Bonding 2. 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

Identifying Minerals

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 Talc: very small Gypsum, Fingernail: 30 Calcite, Penny: 135 Fluorite: 163 Apatite: 430 Feldspar, Glass: 560 Quartz: 820 Topaz: 1340 Corundum: 2100 Diamond: 7000

IDENTIFYING MINERALS (Continued) 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: 0.6-0.9 Gasoline: 0.7, Motor Oil: 0.9 Ice: 0.92 Water: 1.00 Sugar: 1.59 Halite: 2.18 Quartz: 2.65 Most Major Minerals: 2.6-3.0 Aluminum: 2.7

DENSITY Pyrite, Hematite, Magnetite: 5.0 Galena: 7.5 Iron: 7.9 Copper: 9 Lead: 11.4 Mercury: 13.6 Uranium: 19 Gold: 19.3 Platinum: 21.4 Iridium: 22.4 (densest material on Earth)

IDENTIFYING MINERALS (Continued) LUSTER Metallic or Nonmetallic is the most important distinction. Resinous, waxy, silky, etc. are self-explanatory. Vitreous is often used for glassy luster.

IDENTIFYING MINERALS (Continued) 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.

IDENTIFYING MINERALS (Continued) CRYSTAL FORM Takes Luck & Practice Well-formed crystals are uncommon Crystal Classification is somewhat subtle FRACTURE

IDENTIFYING MINERALS (Continued) 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

IDENTIFYING MINERALS (Continued) SPECIAL PROPERTIES Taste, Magnetism, Etc. EXPERIENCE AND READING PROFESSIONAL METHODS Chemical Analysis X-Ray Studies Thin Section

Diffraction

Diffraction

MAJOR MINERAL SUITES ELEMENTS Metallic:Au, Ag, Cu Not Al, Pb, Zn, Fe, etc. Nonmetallic: C - Diamond, Graphite Sulfur

MAJOR MINERAL SUITES SULFIDES: Dense, Usually Metallic Many Major Ores Pyrite FeS2 Chalcopyrite CuFeS2 Galena PbS Sphalerite ZnS2 Molybdenite MoS2

MAJOR MINERAL SUITES HALIDES: Usually Soft, Often Soluble Halite NaCl Fluorite CaF2 SULFATES: Soft, Light Color Gypsum CaSO4 Barite BaSO4

MAJOR MINERAL SUITES 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

Single Chains (Pyroxenes) Inosilicates - Chains Single Chains (Pyroxenes)

Double Chains (Amphiboles) 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

All repeating patterns can be described in terms of repeating boxes 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

Symmetry – the rules behind the shapes

The Crystal Classes