Rock & Mineral Encyclopedia

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

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.

An organic gem formed inside mollusks from layered nacre, prized for its iridescent luster and classic elegance.

A Norwegian larvikite dimension stone prized for its shimmering blue iridescent feldspar crystals.

A Norwegian intrusive rock whose feldspar crystals flash silvery-blue, widely used as blue pearl granite countertops.

A dense, coarse-grained ultramafic rock rich in olivine that makes up most of the Earth's upper mantle.

An opaque, porcelain-white common opal prized for its milky, pearl-like appearance and high porosity, often carved or beaded.

A calcium-magnesium carbonate mineral and rock similar to limestone but harder and only weakly reactive to acid.

A hydrated volcanic glass with pearly, onion-like concentric cracks that pops into lightweight white granules when heated.

A sedimentary rock built from pea-sized concentric spheres called pisoids, often carbonate but sometimes iron or aluminum-rich.

A calcium carbonate mineral and polymorph of calcite, aragonite forms distinctive needle clusters, sea shells, and pearls.

The most common type of mantle peridotite, made of olivine with both orthopyroxene and clinopyroxene, representing fertile upper-mantle rock.

A soft lithium-bearing mica with a lilac to purple color and pearly, flaky sheen, an important ore of lithium.

A dense, dark ultramafic plutonic rock composed almost entirely of pyroxene minerals, often associated with peridotite and layered intrusions.

A glassy, often colorless silicate that forms pyramid-tipped cubes and is famed for its pearly basal cleavage and watery clarity.