Rock & Mineral Encyclopedia

Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.

Gem Silica

A rare, intensely blue chalcedony colored by copper-rich chrysocolla, prized as the most valuable of the blue chalcedonies.

A rare breccia formed by meteorite impact, containing shocked rock fragments and glassy melt blobs welded together.

A vivid copper-bearing Mexican stone of red cuprite and green chrysocolla that evokes a desert sunset.

A metamorphic rock made chiefly of manganese-rich spessartine garnet and quartz, formed from ancient manganese-bearing sediments.

A conglomerate altered by heat and pressure, often with its rounded pebbles stretched and flattened into elongated lenses.

A copper-bearing labradorite feldspar from Oregon, famous for its range of natural colors and glittery aventurescent copper schiller.

A rare granitic rock containing concentric, onion-like spheres called orbicules, prized as a striking ornamental stone.

A dark, organic-rich shale loaded with kerogen and bitumen that can yield oil and gas, often finely laminated and combustible.

A granite-like rock containing orthopyroxene, formed at high temperatures and pressures and often classed with the granulites.

Tourmaline in blue tones, encompassing iron-colored indicolite and the rare neon copper-bearing Paraiba, among the scarcer tourmaline colors.

A soft, dark, organic-rich mud deposited in stagnant, oxygen-poor water, a key precursor to oil and gas source rocks.

A green ornamental stone, often serpentine-rich marble or verde antique, valued for its rich green color and white veining.

A schist derived from clay-rich sediments, rich in mica and often bearing index minerals like garnet, staurolite, or kyanite.