Rock & Mineral Encyclopedia

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

Velvet Obsidian

A black volcanic glass with a soft, velvety internal sheen caused by aligned microscopic inclusions catching the light.

Opal showing a smooth, silky satin-like sheen across its surface, valued for a gentle, refined luster.

Hardened, fine-grained mudrock intermediate between shale and slate, dense and non-fissile, often carved into ornaments.

A fine-grained sedimentary rock of compacted clay and silt that, unlike shale, breaks in blocks rather than thin layers.

The most common sedimentary rock, a fissile mudrock of compacted clay and silt that splits into thin layers.

A golden-brown chatoyant quartz with a shimmering silky band of light, formed when quartz replaces fibrous crocidolite.

A fine-grained foliated metamorphic rock between slate and schist, recognized by its silky silvery sheen and wavy, crinkled surfaces.

An old varietal name for alkali- and cesium-rich beryl, typically colorless to pale pink, overlapping with vorobyevite and morganite.

The calcium-aluminum garnet species spanning green tsavorite, cinnamon hessonite, and colorless leuco garnet — one of the most varied garnets.