Rock & Mineral Encyclopedia

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

Emerald in Matrix

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

A granite-like rock containing orthopyroxene, formed at high temperatures and pressures and often classed with the granulites.

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

A rare granitic rock containing concentric, onion-like spheres called orbicules, prized as a striking ornamental stone.

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

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

A hard, fine-grained siliceous rock with a dull porcelain-like texture, intermediate between soft diatomite and dense chert.

Quartz colored blue by inclusions of the mineral dumortierite, giving a denim-like blue ornamental stone harder than dumortierite alone.