Rock & Mineral Encyclopedia

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

Greenstone

A general field term for green, low-grade metamorphosed basaltic rocks colored by chlorite, epidote, and actinolite.

Basalt that has been metamorphosed, developing new minerals like chlorite, actinolite, and epidote that give it a greenish color.

A tough, dark, medium-grained igneous rock with the composition of basalt, common in dikes and sills.

A green, foliated low-grade metamorphic rock colored by chlorite, actinolite, and epidote, marking the greenschist metamorphic facies.

A green-and-white volcanic breccia from Vancouver Island, cemented by jasper and rich in epidote, popular as a regional lapidary stone.

Glacially deposited banded agates found along Lake Michigan beaches, small waterworn pebbles with concentric red and grey banding.