Petzite. A heavy black or steel gray metallic telluride ore of gold and silver (Ag₃AuTe₂).
Placer. A sand or gravel deposit containing particles or nuggets of gold or other heavy valuable minerals.
Plateau. An elevated, comparatively flat surface of land, usually larger than a [mesa], sometimes composed of many mesas, and often dissected by deep stream valleys.
Porphyry. An igneous rock, usually intrusive, which contains conspicuous large crystals in a fine-grained matrix.
Pyrite. A brass-yellow metallic mineral (FeS₂) that is an important source of sulfur. It is commonly known as fool’s gold.
Reef. A moundlike limestone structure built in the sea by sedentary organisms such as corals.
Rhyolite. A light-colored volcanic rock with quartz and [feldspar] as the principal constituents.
Schist. A [metamorphic rock] characterized by parallel orientation of flat-grained minerals like mica.
Sedimentary rocks. Rocks formed of fragments of other rock transported by wind or water, or formed by precipitation from solution.
Sphalerite. An amber-yellow to black mineral (ZnS) that is an important ore of zinc.