Book excerpt: Earth's outer crust Geologists Time and rock units Geologic map What are rocks and minerals? Chemical elements Minerals Rocks Igneous rocks Extrusive or volcanic igneous rocks Intrusive igneous rocks Sedimentary rocks Soils Sedimentary rock materials in broken fragments Sedimentary rock materials in solution Cementing materials and chemical sediments Sedimentary rocks formed by plants and animals Metamorphic rocks Static metamorphism Contact metamorphism Dynamic metamorphism Occurrence and properties of minerals How minerals occur Crystalline minerals Crystals Imperfect crystals Amorphous minerals Some distinguishing properties of minerals Color Luster Transmission of light Hardness Streak or powder Cleavage Parting Fracture Specific gravity Effervescence in acid Some special occurrences of minerals Cave deposits Concretions Geodes Petrified wood Collecting rocks and minerals Rock and mineral identification charts How to use the mineral identification charts Key to mineral identification charts Mineral identification charts How to use the rock identification charts Rock identification charts Descriptions of some Texas rocks and minerals Anhydrite Asbestos Barite Basalt Calcite Cassiterite Celestite Cinnabar Clay Copper minerals (chalcocite, chalcopyrite, malachite, azurite) Dolomite Feldspar Fluorite Galena Garnet Gneiss Gold Granite Graphite Gypsum Halite Hematite Limestone Limonite Llanite Magnetite Manganese minerals (braunite, hollandite, pyrolusite) Marble Mica Obsidian and vitrophyre Opal Pegmatite Pyrite Quartz Quartzite Rhyolite Sand and sandstone Schist Serpentine Shale Silver minerals (argentite, cerargyrite, native silver) Sulfur Talc and soapstone Topaz Tourmaline Uranium minerals (carnotite, uranophane, pitchblende) Volcanic ash (pumicite) Composition, hardness, and specific gravity of some Texas minerals Books about rocks and minerals Nontechnical books for beginners Textbooks and other reference books Selected references on Texas rocks and minerals