Rock & Mineral Encyclopedia

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

Tactite

A contact-metasomatic calc-silicate rock, essentially a skarn, formed where intrusions react with carbonate rocks and often host ore.

A calc-silicate rock formed by chemical exchange between magma and carbonate rock, often rich in garnet and economically important ore minerals.

Deeply saturated green tourmaline colored by iron, often so dark it appears nearly black until viewed in bright light.

Obsidian in gray tones, often semi-translucent, colored by light scattering and minor inclusions within the volcanic glass.