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Physical Properties of Minerals. 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 .
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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 • 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: 0.001Wood - 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: 5.0Galena: 7.5Iron: 7.9Copper: 9Lead: 11.4Mercury: 13.6Uranium: 19Gold: 19.3Platinum: 21.4Iridium: 22.4 (densest material on Earth)
Density is Extremely Consistent NaCl Mol Wt. = 22.99 (Na) + 35.45 (Cl) = 58.44 Cl: 8 at corners of unit cube shared 8 ways. 8 x 1/8=1 Cl: 6 in centers of cube face shared 2 ways, 6 x ½ = 3 4 Cl per unit cell Na: 12 along edges shared 4 ways, 12 x ¼ = 3 Na: One in center of cell 4 Na per unit cell.
Density is Extremely Consistent Mol. Wt of a unit cell of NaCl = 4 x 58.44 = 233.76 233.76 gm of NaCl = 6.02 x 1023 unit cells One unit cell = 233.76 gm/ 6.02 x 1023 = 38.83 x 10-23 gm Unit cell = .564 nm on a side Unit cell volume = .1794 x10-27 m3 = 17.94 x10-23 cm3 Density = 38.83 x 10-23 gm/17.94 x10-23 cm3 = 2.164 gm/cm3 Textbook value: 2.16 gm/cm3
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.
Parting • Related to Cleavage • Occurs Along Specific Atomic Planes • Not Present in All Cases • Due to Impurities, Inclusions Along Atomic Plane • Common in Quartz, Magnetite
Identifying Minerals (Continued) Crystal Form • Takes Luck & Practice • Well-formed crystals are uncommon • Crystal Classification is somewhat subtle Fracture • Conchoidal = Curving, smooth (Glass, etc.)
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
