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 Topaz

A durable blue silicate gem, mostly produced by treating colorless topaz, popular for its bright color and affordability.

The blue gem variety of corundum, prized for its rich color, extreme hardness, and brilliance second only to diamond.

The deepest, most saturated blue grade of treated topaz, prized for its rich steely-blue color and durability in jewelry.

The gem variety of corundum in every color except red, most prized in velvety blue and exceptionally hard and durable.

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