Rock & Mineral Encyclopedia

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

Amphibolite

A dark, dense metamorphic rock dominated by hornblende and plagioclase, formed by medium- to high-grade metamorphism of basalt.

A plagioclase feldspar famous for labradorescence, a dramatic flash of iridescent blue, green, and gold across a dark gray stone.

A dark jasper trade stone speckled with pale flecks resembling a starry night sky, valued for its cosmic appearance.

Precious opal from the Mintabie field in South Australia, known for hard, bright crystal opal and some dark-bodied stones.