Rock & Mineral Encyclopedia

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

Cataclasite

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

A striking platy, blade-like variety of albite feldspar that grows in fanned aggregates of thin white crystals within granite pegmatites.

A common rock-forming potassium feldspar, the Mohs hardness reference at 6, found in granites and used in ceramics and glassmaking.

A feldspar-rich sandstone, often pink, that points to granitic source rocks eroded quickly in dry or cold climates.

An extremely rare rubidium-dominant alkali feldspar, the rubidium analogue of microcline, found in rare-element granitic pegmatites.

A trade name for high-brilliance golden grossular-andradite (grandite) garnet, most associated with the Mali deposits of West Africa.

A rare grossular-andradite blend ('grandite') from Mali, prized for its high brilliance and golden-green to yellow color.

A high-grade metamorphic gneiss of garnet, sillimanite, quartz, and graphite, derived from ancient aluminous sediments.

Abundant banded chalcedony from southern Brazil, the world's main source of agate slices and dyed agate products.

An intermediate plutonic rock with nearly equal alkali and plagioclase feldspar and very little quartz, sitting between diorite and syenite.

A silver-white iron arsenic sulfide and the most common arsenic mineral, known for striking sparks and a garlic smell when struck.

A porous sedimentary rock naturally saturated with bitumen, dark, tarry-smelling, and historically mined for paving.

Molybdenite is the primary ore of molybdenum, a soft, greasy, silver-gray sulfide that closely resembles graphite.

A hydrated volcanic glass with pearly, onion-like concentric cracks that pops into lightweight white granules when heated.