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 jasper made of angular fragments naturally cemented back together, typically showing red and brown pieces in a quartz matrix.

Syrian Garnet is an old trade name for fine deep-red almandine, historically tied to the Syriam region and prized as 'precious garnet.'

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

A rare black carbon-rich rock from Russia, noted for containing fullerenes and ranging from dull mineralized stone to lustrous noble shungite.

A durable magnesium aluminum oxide gem that occurs in many colors and was long mistaken for ruby.

The classic gem opal that flashes shifting spectral colors, defined by the diffraction effect known as play-of-color.

A group of green magnesium silicate minerals with a smooth, waxy feel, often carved and sometimes sold as imitation jade.

The rarest and most valuable opal, with a dark body tone that makes its flashing rainbow play-of-color blaze brilliantly.

The most common precious opal, with a pale milky body that shows softer pastel flashes of play-of-color throughout.

Opal from Australia, the world's leading source of precious opal, ranging from white and crystal to prized black and boulder types.