Mineral Formation + Ore Notes

How Minerals Form

• Minerals need = time, space, fluids, temperature, and pressure

• Key to formation = chemical ingredients to make minerals be present

  • formation of minerals = formation of rocks

  • mineral: solid, natural, inorganic, definite crystal structure, definite chemical composition

  • rock: composed of one or more mineral, and/or organic matter

• Mineral Resource:

  • rock that’s enriched with metallic or non-metallic minerals

    • metallic: metals

      • hematite (iron—>steel), gold, silver, tin, copper

    • non-metallic: no metals

      • sand, salt, fluorite, uraninite, clay, gravel, limestone, coal

• Ore:

  • concentration of metallic or rare earth elements that can be used for profit

Types of Formation

• A. Precipitation: forms from a fluid (H20 or CO2)

  • hypo-thermal (hot water) = one deposit (metallic minerals) and quartz

    • precious metals, gold, silver, etc.

  • evaporation: salts (halite)

  • other examples: geodes, halite, gypsum, cave deposits

• B. Sublimation: 2 forms from vapor (directly from a gas)

  • ex: volcanic vents, sulfur

• C. Crystallization: forms from cooling/crystallization of magma or lava

  • ex: quartz, feldspar, mica, and hornblende in igneous rocks

• D. Solid State: formed from other solids

  • ex: metamorphism: forming garnet, kyanite, serpentine

  • diagenesis: chemical or physical changes during sedimentation (clay, quartz)

  • weathering: oxidation forming iron oxides

• E. Biological Activity: organisms secrete calcium carbonate shells

  • ex: calcite

Mineral Forming Environments

• A. Igneous

  • Plutonic: slow crystallization beneath the surface which can produce large crystals

  • Volcanic: faster crystallization on the surface which can produce smaller crystals

• B. Sedimentary

  • Clastic: lithification of rocks debris and fragments (gravel, sand, silt, clay)

    • ex: conglomerates, sandstone, shale

  • Placer: stable minerals carried in rock debris by wind, water, ice

    • ex: gold

  • Biological: organisms precipitate calcium carbonate

    • calcite

  • Chemical: minerals form out of solution

    • ex: salts form out of evaporation process

• C. Metamorphic = heat and pressure

  • Contact: heat and chemically active fluids (marble)

  • Regional: high temps and high pressure via mountain building and folding

  • Hydrothermal: hot fluids precipitate minerals in fractures or veins (metallic minerals)

Mineral Resources vs Ores

• Mineral Resource

  • volume of rock enriched in one or more useful minerals

    • metallic: gold, silver, copper, lead, iron

    • non-metallic: sand, gravel, halite, uranium

• Some minerals require processing after being found and others do not

• Ore deposits

  • concentrations of metallic minerals or rare earth elements that can be mined for profit

    • origin: magmatic, sedimentary, hydrothermal, placer, residual

      • ore ex: bauxite (aluminum), hematite (iron), galena (lead), sphalerite (zinc), acurite (copper)