Rock & Mineral Encyclopedia

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

Gold

A dense, soft, intensely yellow native metal valued for millennia in coinage, jewelry, and electronics.

A hard, tough metamorphic rock of fused quartz grains, formed by recrystallizing quartz sandstone under heat and pressure.

Sandstone altered by metamorphism, with partly recrystallized quartz grains, transitional between true sandstone and quartzite.

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

Rhyolite that has been metamorphosed, recrystallizing its silica-rich volcanic material into a tougher felsic metamorphic rock.

Coarse-grained gabbro that has been metamorphosed, partly recrystallizing into amphibole, plagioclase, and other metamorphic minerals.

A dense, opaque black variety of microcrystalline quartz historically used as a touchstone for testing precious metals.

A pale copper-red nickel arsenide, historically called kupfernickel, that is an ore of nickel and gives the metal its name.

Tin oxide and the principal ore of tin, a dense, hard mineral mined since the Bronze Age for tin metal.