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Minerals are the Chemicals that make up the Earth
• NATURALLY-OCCURRING
• INORGANIC
• CHEMICAL COMPOUNDS
• ABOUT 3000 KNOWN
• 200 COMMON
• 20 ROCK-FORMING
Atomic Bonding2. ELECTRICAL NEUTRALITY• (+) and (-) Cancel Out
3. BONDING (SATISFY 1 & 2)• Ionic (NaCl) • Covalent (O2) • Metallic (Cu, Al, Fe) • Hydrogen (in water)
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
NAMING MINERALS COLOR• Glauconite (Greek: Glaucos = Blue-green) OTHER PROPERTIES, USES• Magnetite COMPONENTS• Chromite PLACES• Muscovite (Moscow) PEOPLE• Biotite
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
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
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: 0.6-0.9Gasoline: 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)
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
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 MetallicMany 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
Phyllosilicates - Sheets
Si2O5 sheets with layers of Mg(OH)2 or Al(OH)3
• Micas
• Clay minerals
• Talc
• Serpentine (asbestos) minerals