Rock & Mineral Encyclopedia

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

Calcilutite

A very fine-grained, mud-sized limestone formed from carbonate mud, smooth and dense with conchoidal fracture.

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

A banded, porous limestone deposited by mineral springs, prized as a warm-toned natural building and tile stone.

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 famous white to blue-grey Italian marble from Carrara, prized for centuries by sculptors and architects for its purity and fine grain.

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

A fractured fine-grained limestone whose iron-stained crack networks form natural scenes resembling ruined cities and landscapes.

A metamorphic rock of calcium-rich silicate minerals formed from impure limestone or dolomite altered by heat and fluids.

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