Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Skutterudite
A metallic cobalt-nickel arsenide, an important cobalt ore, named for the Skutterud mines of Norway.
mineralFlame Opal
A glowing orange-to-red opal whose warm body color resembles flame; some stones add flashes of play-of-color.
gemstone
Uraninite
Uraninite is the chief radioactive uranium ore, a dense black oxide and the historic source of radium and uranium.
mineral
Dunite
An ultramafic intrusive rock made almost entirely of olivine, representing mantle material.
igneous
Talc
The softest mineral on the Mohs scale, talc has a greasy, soapy feel and is the source of talcum powder and soapstone.
mineral
Psilomelane
A field term for hard black massive manganese oxides, often botryoidal, mined as an important manganese ore.
mineral
Peridot
The gem-quality green variety of olivine, peridot is colored by iron and is one of the few gems found in only one color.
gemstone
Peruvian Pink Opal
A soft pink common opal from the Peruvian Andes, prized for its opaque rosy color rather than play-of-color.
gemstone
Lavender Opal
A pastel purple variety of common opal, valued for its gentle lilac body color rather than any play-of-color.
gemstone
Itabirite
A metamorphosed banded iron formation of alternating quartz and iron-oxide layers, mined as a major iron ore.
metamorphic
Peridotite
A dense, coarse-grained ultramafic rock rich in olivine that makes up most of the Earth's upper mantle.
igneous
Star Opal
Opal that displays a radiating, star-shaped pattern of play-of-color, a rare and prized internal structure.
gemstonePaintbrush Jasper
A scenic jasper whose flowing streaks of warm color resemble strokes left by a loaded paintbrush.
mineral
Blue Opal
A soft blue common opal, famously from Peru, valued for its serene sky-to-teal color rather than play-of-color.
gemstoneEulysite
A rare, dense iron-rich metamorphic rock composed of fayalite, iron pyroxene, and almandine garnet.
metamorphic
Carnotite
A bright yellow, radioactive potassium uranyl vanadate that is a major ore of both uranium and vanadium.
mineralSpiderweb Obsidian
Black volcanic glass crossed by a fine network of grey or brown veins that resemble a spider's web.
igneous
Chlorite Schist
A soft, green, foliated rock rich in chlorite, formed by low-grade metamorphism of mafic or volcanic rocks.
metamorphic
Pyrolusite
A black manganese dioxide mineral that is the most important ore of manganese and a source of black pigment and dendrites.
mineral
Champagne Tourmaline
A soft brown to golden-brown tourmaline with warm, neutral tones reminiscent of sparkling champagne.
gemstone
Prasiolite
A pale green variety of quartz, usually created by heat-treating amethyst, often marketed as green amethyst.
gemstone
Achroite
The rare colorless variety of tourmaline, named from the Greek for 'without color' and prized by collectors.
gemstone
Velvet Opal
Opal with a soft, velvety surface sheen rather than sharp play-of-color, prized for its gentle glow.
gemstone
Angelite
A soft pale-blue calcium sulfate, the anhydrous form of gypsum, prized as a gentle, calming tumbled stone.
mineral