Rock & Mineral Encyclopedia

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

Granodiorite

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

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

A chromium-rich pyrope garnet whose intense blood-red color comes from chromium, often mined from ant hills and kimberlite weathering.

A nodular rhyolite geode-like ball whose plain exterior hides a star-shaped agate or chalcedony core when cut.

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.