Rock & Mineral Encyclopedia

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

Thulite

A pink, manganese-rich variety of zoisite used as an ornamental gemstone, often mottled with white quartz and grey matrix.

A combustible black sedimentary rock formed from ancient plant matter and burned for centuries as a primary fossil fuel.

A soft, lightweight siliceous sedimentary rock made of fossil diatom remains, prized as a fine natural abrasive and polishing powder.

A jasper made of angular fragments naturally cemented back together, typically showing red and brown pieces in a quartz matrix.

A cohesive fault rock formed by brittle crushing and grinding of rock along a fault zone, with angular fragments in a fine matrix.

A prized blue to blue-green copper-aluminium phosphate, often veined with dark matrix, treasured for jewelry across many cultures.

A very fine-grained limestone made of microcrystalline calcite mud, dense and smooth, deposited in calm carbonate settings.

A metamorphosed limestone of interlocking calcite crystals, prized for sculpture and architecture for its workability and polish.

Sand-grained limestone composed of carbonate particles such as shell fragments and ooids cemented into a calcite rock.

A calcium-magnesium tourmaline that forms in metamorphosed limestones, typically dark green to brown and often in well-formed crystals.