Rock & Mineral Encyclopedia

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

Pseudotachylite

A dark, glassy rock formed when frictional heat from fault movement or impact melts rock along narrow veins.

The fine white marble of Mount Pentelikon used to build the Parthenon, famous for the golden patina it develops with age.

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