Rock & Mineral Encyclopedia

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

Talc Schist

An extremely soft, soapy-feeling foliated rock made largely of talc, formed by metamorphism of magnesium-rich rocks.

A foliated metamorphic rock dominated by glittering dark biotite mica, formed from mudstones under medium-grade regional metamorphism.

A foliated metamorphic rock of calcite mixed with mica, quartz, and calc-silicate minerals, derived from marly sediments.

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

A coarse-grained mafic plutonic rock similar to gabbro but with orthopyroxene as the dominant pyroxene instead of clinopyroxene.

A dark, mineral-rich dike rock with abundant mica or amphibole phenocrysts set in a fine groundmass, often associated with gold and diamonds.

A soft, fine-grained, translucent form of gypsum (or banded calcite) long prized as a carving and ornamental stone.

A coarse-grained intrusive igneous rock dominated by alkali feldspar with little or no quartz.

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

Extremely fine-grained, even-textured limestone famous for lithographic printing and for preserving exquisite fossils like Archaeopteryx.

A common coarse-grained intrusive rock like granite but richer in plagioclase than potassium feldspar.

A dark, foliated schist rich in needle-like hornblende crystals, formed by metamorphism of mafic igneous rocks.