Minerals

Composition of the Sun

Abundance of Light Elements Rarity of Lithium, Beryllium, Boron Preference for Even Numbers Abundance peak at Iron, trailing off after

How Elements Form in Stars Sun: 4 H  He He + particle  Mass 5 – Unstable He + He  Mass 8 – Unstable He + He + He  C Add more He to make heavier elements End of the line is iron for energy production Atoms beyond Iron made in massive stars

What are Planets Made of? Same material as Sun Minus the elements that remain mostly in gases We find this pattern in a certain class of meteorites

Chondrites

The Earth’s Crust looks Very Different

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 (O 2 ) 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 FeCl 2 : Light Green, Water Soluble FeSO 4 : Light Green, Water Soluble FeCO 3 : Brown, Fizzes in Acid FeS 2 : Dense, Brittle, Metallic, Cubic Crystals

On the Other Hand, Sulfides have Many Properties in Common FeS 2 CuFeS 2 PbS ZnS 2 All are Dense, Brittle, Metallic, have Cubic Crystals

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: Fluorite: Apatite: Feldspar, Glass: Quartz: Topaz: Corundum: Diamond: 7000

IDENTIFYING MINERALS (Continued) DENSITY Directly related to masses of component atoms and their spacing Usually very consistent

DENSITY - gm/cm 3 (weight relative to water ) Air: Wood - Balsa: 0.1, Pine: 0.5, Oak: 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: 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

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 FeS 2 Chalcopyrite CuFeS 2 Galena PbS Sphalerite ZnS 2 Molybdenite MoS 2

MAJOR MINERAL SUITES HALIDES: Usually Soft, Often Soluble Halite NaCl Fluorite CaF 2 SULFATES: Soft, Light Color Gypsum CaSO 4 Barite BaSO 4

MAJOR MINERAL SUITES OXIDES: Often Variable, Some Ores Hematite Fe 2 O 3 Bauxite Al(OH) 3 (a hydroxide) Corundum Al 2 O 3 (Ruby, Sapphire) CARBONATES: Fizz in Acid, Give off CO 2 Calcite CaCO 3 Dolomite CaMg (CO 3 ) 2

MOST IMPORTANT MINERAL SUITE: The Silicate Minerals Si + O = 75% of Crust Silicates make up 95% + of all Rocks SiO 4 : -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

Si 2 O 5 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