Rock & Mineral Encyclopedia

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

Blue Kyanite

A striking blue aluminum silicate famous for bladed crystals and anisotropic hardness that differs dramatically along and across the blade.

A bladed aluminosilicate famous for having two very different hardnesses depending on the direction you scratch it.

A mica schist containing bladed blue kyanite crystals, a marker of medium- to high-grade metamorphism of aluminous rocks.