Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Millerite
A nickel sulfide famous for delicate brass-yellow hairlike crystals that form radiating sprays inside cavities and geodes.
mineral
Yellow Obsidian
Yellow to golden volcanic glass; natural examples owe their color to iron, though much bright yellow obsidian on the market is manufactured glass.
igneous
Tantalite
A dense black iron-manganese tantalate that is the chief ore of tantalum, forming a series with columbite and mined as coltan.
mineral
Molybdenite
Molybdenite is the primary ore of molybdenum, a soft, greasy, silver-gray sulfide that closely resembles graphite.
mineral
Honey Calcite
A warm golden-to-amber variety of calcite, a soft calcium carbonate mineral valued for its honeyed glow and easy carving.
mineral
Uraninite
Uraninite is the chief radioactive uranium ore, a dense black oxide and the historic source of radium and uranium.
mineral
Tetrahedrite
A gray copper-antimony sulfosalt of the fahlore group, an important ore of copper and often silver, forming tetrahedral crystals.
mineral
Malachite
A vivid green copper carbonate mineral famous for swirling concentric bands, used as an ore of copper and an ornamental gemstone.
mineral
Golden Feldspar
A trade name for golden-yellow gem feldspars, including golden orthoclase, golden sunstone, and golden labradorite.
gemstone
Goldmanite
A green, vanadium-dominant garnet that forms in vanadium-rich metamorphic and sedimentary rocks, notably in uranium-vanadium districts.
mineral
Wulfenite
A lead molybdate mineral famous for thin, brilliant orange to yellow tabular crystals, prized by collectors and an ore of molybdenum.
mineral
Cerussite
A dense lead carbonate mineral forming brilliant colorless to white crystals, an important ore of lead and a favorite of collectors.
mineral
Anglesite
A heavy lead sulfate secondary mineral, often colorless to white with adamantine luster, formed by the oxidation of galena.
mineral
Mariposite
A green, gold-associated metamorphic rock made of chrome-rich mica and quartz, named for Mariposa County in California's gold country.
metamorphic
Oregon Opal
Opal from Oregon, USA, ranging from translucent blue Owyhee opal to clear and fiery contra-luz precious opal from Opal Butte.
gemstone
Stibnite
Stibnite is the chief ore of antimony, famous for its dramatic clusters of bladed, silvery-gray metallic crystals.
mineral
Erythrite
A soft pink to crimson hydrated cobalt arsenate, famous as cobalt bloom that signals nearby cobalt ores.
mineral
Bastnasite
A rare-earth fluorocarbonate that is one of the world's most important ores of cerium, lanthanum, and other rare earth elements.
mineral
Orendite
A rare ultrapotassic lamproite carrying sanidine, phlogopite and diopside, classically from Wyoming's Leucite Hills.
igneous
Spodumene
Spodumene is a lithium aluminum silicate that is both a major lithium ore and the source of gem kunzite and hiddenite.
gemstone
Wolframite
Wolframite is the historic principal ore of tungsten, a heavy black tungstate forming bladed crystals in granite veins.
mineral
Stephanite
A black metallic silver antimony sulfide, historically a notable silver ore known as brittle silver ore.
mineral
Hematite
The principal iron ore, a heavy iron oxide ranging from metallic silver-gray to earthy red, always leaving a tell-tale red-brown streak.
mineral
Franklinite
A black spinel-group zinc iron oxide, essentially unique to Franklin, New Jersey, where it was a key zinc and manganese ore.
mineral