Rock & Mineral Encyclopedia

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

Halite

The natural mineral form of table salt, a soft, water-soluble evaporite that forms perfect cubic crystals and tastes salty.

A clear, soft crystalline variety of gypsum that forms glassy or fibrous wands, so soft it can be scratched with a fingernail.

A very soft sulfate mineral defining Mohs 2, occurring as selenite, satin spar, alabaster, and desert rose, used to make plaster.

A soft sedimentary evaporite made of massive gypsum, deposited when sulfate-rich seawater or lake water evaporates and concentrates.

Aquamarine crystals still attached to their natural host rock, prized as mineral specimens showing beryl in its original pocket setting.

Natural emerald crystals still embedded in their host rock, prized as mineral specimens that show how the gem grew in place.

The natural crystalline form of emerald, the prized green chromium-and-vanadium variety of beryl and the May birthstone.

A rosette-shaped cluster of bladed gypsum or barite crystals that traps sand, forming flower-like formations in arid deserts.

Precious opal from the Andamooka field of South Australia, famous for solid crystal opal and its distinctive treatable matrix opal.

A poorly sorted, muddy sandstone with abundant clay matrix between its grains, typically dark and deposited by turbidity currents.

A lithified glacial till, a poorly sorted rock of mixed boulders, pebbles and fine matrix that records ancient glaciations.

A rounded sedimentary nodule cracked internally and filled with veins of yellow calcite, prized for its striking dragon-skin patterning.

A hard, dark, poorly sorted sandstone with a muddy matrix, typically deposited by underwater turbidity currents.