Talc Gray, NM 1 Green, Hydrous green gray, greasy/soapy magnesium white silicate Hematite Reddish M to 1 6.5 Red Heavy Iron oxide – brown, steel NM gray Gypsum Gray, NM 2 White to Hydrous calcium colorless colorless sulfate Muscovite White, NM 2 3 White to Thin flakes – mica colorless colorless silicate Biotite Black, NM 2 3 White to Thin flakes Ferromagnesium – mica brown, dark colorless silicate green Galena Silver gray M 2.5 Grayish Heavy, cubic Lead sulfide black Halite Colorless, NM 2.5 White to Tastes salty, Sodium chloride white, colorless cubic yellow, pink Fluorite Purple, blue, NM 4 White to Interlocking Calcium fluoride green colorless cubes Magnetite Silver black M 6 Black Magnetic, Iron oxide heavy Pyrite Brassy M 6 6.5 Greenish Gold-like, Iron sulfide – yellow black heavy Quartz Colorless, NM 7 White to 6-sided Silicon white, colorless crystals variable Part 2 Rock Identification – Rocks are composed of two or more minerals and can be classified as igneous, sedimentary, or metamorphic based on origin. Igneous rocks form when magma rises from the mantle, cools, and hardens either below the Earth’s surface or on the surface. Sedimentary rocks are layered accumulations of mineral particles derived from weathering and erosion of preexisting rocks, chemical deposition, or accumulation of plant and animal remains. Metamorphic rocks form when igneous, sedimentary, or other metamorphic rocks are subjected to intense heat and pressure to form Igneous Rock Identification Igneous rocks can be subdivided based on whether they formed above or below the Earth’s surface. Intrusive igneous rocks form by gradually cooling below the surface, which results in the formation of large crystal grains. Extrusive igneous rocks form by cooling rapidly at the Earth’s surface, which results in small crystal grains and often contain pockets of air.
Talc Gray, green NM 1 Green, gray, white greasy/soapy Hydrous magnesium silicate Hematite Reddish brown, steel gray M to NM 1 – 6.5 Red Heavy Iron oxide Gypsum Gray, colorless NM 2 White to colorless Hydrous calcium sulfate Muscovite mica White, colorless NM 2 – 3 White to colorless Thin flakes silicate Biotite mica Black, brown, dark green NM 2 – 3 White to colorless Thin flakes Ferromagnesium silicate Galena Silver gray M 2.5 Grayish black Heavy, cubic Lead sulfide Halite Colorless, white, yellow, pink NM 2.5 White to colorless Tastes salty, cubic Sodium chloride Fluorite Purple, blue, green NM 4 White to colorless Interlocking cubes Calcium fluoride Magnetite Silver black M 6 Black Magnetic, heavy Iron oxide Pyrite Brassy yellow M 6 – 6.5 Greenish black Gold-like, heavy Iron sulfide Quartz Colorless, white, variable NM 7 White to colorless 6-sided crystals Silicon Part 2 – Rock Identification Rocks are composed of two or more minerals and can be classified as igneous, sedimentary, or metamorphic based on origin. Igneous rocks form when magma rises from the mantle, cools, and hardens either below the Earth’s surface or on the surface. Sedimentary rocks are layered accumulations of mineral particles derived from weathering and erosion of preexisting rocks, chemical deposition, or accumulation of plant and animal remains. Metamorphic rocks form when igneous, sedimentary, or other metamorphic rocks are subjected to intense heat and pressure to form Igneous Rock Identification Igneous rocks can be subdivided based on whether they formed above or below the Earth’s surface. Intrusive igneous rocks form by gradually cooling below the surface, which results in the formation of large crystal grains. Extrusive igneous rocks form by cooling rapidly at the Earth’s surface, which results in small crystal grains and often contain pockets of air.