Rock & Mineral Encyclopedia

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

Hyalite Opal

A clear, glassy, botryoidal common opal famous for its intense green fluorescence under UV light, caused by trace uranium.

A transparent yellow to golden gem variety of labradorite feldspar, usually faceted to show its clear, warm color.

Translucent smoky-gray obsidian that transmits a hazy light, intermediate between clear and fully black volcanic glass.

Opal from Oregon, USA, ranging from translucent blue Owyhee opal to clear and fiery contra-luz precious opal from Opal Butte.