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Minerals

Minerals. Review:. Rocks are made of minerals, minerals are made of elements, what are elements made of?. Minerals have crystalline structure. Repeating patterns of atoms give minerals their crystal form. Minerals. Naturally occurring Solid substance

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Minerals

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  1. Minerals

  2. Review: Rocks are made of minerals, minerals are made of elements, what are elements made of?

  3. Minerals have crystalline structure • Repeating patterns of atoms give minerals their crystal form

  4. Minerals • Naturally occurring • Solid substance • Orderly and repetitive crystalline structure • Definite chemical composition • Generally considered inorganic (shells are minerals; sugar is not)

  5. How Minerals Form • Everywhere, different conditions • Deep in crust or mantle (silicates) • Warm, shallow seas (limestone) • At or near surface from weathering (clay) • In crevices

  6. Processes that Form Minerals • Crystallization from magma (changes in pressure and temperature within the magma) • Precipitation • Changes in pressure and temperature (forces working at different depths) • Formation from hydrothermal solutions

  7. How They Form • As magma cools, minerals from at different temperatures (some at hottest temp, some at coolest temp) • Water contains dissolved substances; as H2O evaporates, minerals can form. Changes in T can cause minerals to precipitate out (limestone and halite) • Mica forms from changes inpressure (recrystallize while still solid) and temperature (destabilizes mineral) • Hot water and dissolved substances (hydrothermal solution) come in contact with minerals, chemical reactions create new minerals (quartz and pyrite); hot springs, hydrothermal vents, and volcanoes (sulfur) • Bacteria and rock interactions – sulfur (anaerobic bacteria and sulfate, ex gypsum); gold?; banded iron? Bacteria used to extract ores

  8. Properties of Minerals • Color – obvious, but not always reliable because of impurities (different colors in quartz) • Streak – color in powdered form • Luster – how light reflects from surface • Crystal Form – visible expression of internal arrangement of atoms • Hardness – resistance to being scratched • Cleavage – tendency to cleave or break along flat, even surface (broken pieces will retain geometry) • Fracture – uneven breakage of mineral (no cleavage); pieces show no internal geometry • Density – ratio of mass to volume • Specific gravity – ratio of its mass to an equal volume of water

  9. Special Properties • Magnetism – (magnetite) • Double refraction – (calcite) • Fizzing in hydrochloric acid – calcite, dolomite • Feel – greasy? (talc) • Smell – (sulfur) • Taste – (salty-halite)

  10. Crystalline Form Perfect: if “space” for a crystal to grow. Limited space, little growth, but still internal crystalline structure

  11. Rock-Forming minerals • Eight minerals comprise most of the materials in Earth’s crust. About a dozen are most common (out of thousands) • Minerals are divided into two groups based on composition • Silicates – most common on Earth • Non-silicates

  12. Silicates • The elements silicon and oxygen make up 75% of earth’s continental crust • Most common mineral group based on silicon-oxygen tetrahedron - SiO4 • Examples: Feldspar (most common mineral); mica

  13. Non-silicates • Make up only 25% of continental crust • Many are economically important ($$$) • Subdivided into: Carbonates (-CO3), iron oxides (-O), sulfides (-S) and sulfates (-SO3), halides (salt), and native element minerals (C, S, Au)

  14. Carbonates • Second most common mineral • carbon and oxygen and one or more metallic elements e.g. Calcium, as in calcite (CaCO3. Dolomite contains magnesium and calcium). • Both “fizz” with HCl acid (CO2 forms from reaction causing the “soda” like “fizz”) • Limestone and marble made of carbonate minerals

  15. Carbonate (Limestone, dolomite) White Cliffs of Dover (“chalk” from Cretaceous) Calcite: Carbonate

  16. Oxides, Sulfides,Sulfates • Economically important ex: lead ore, iron ore • Oxide=Metal+Oxygen ex: hematite, magnetite • Sulfate= metal, oxygen + sulfur ex: gypsum • Sulfide=metal+sulfur ex: pyrite, galena

  17. Other non-silicates Halides ex. Salt Native elements ex. Gold, silver, copper, diamond, graphite, platinum, sulfur

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