Rock & Mineral Encyclopedia

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

Red Agate

A red-toned banded chalcedony colored by iron oxides, ranging from natural carnelian-like reds to heat-treated stones.

A warm golden-to-amber opal ranging from translucent common opal to precious stones that flash play-of-color over a honey body.

Precious opal from the Mintabie field in South Australia, known for hard, bright crystal opal and some dark-bodied stones.

A golden-toned opal ranging from translucent common opal to precious stones flashing color against a warm yellow body.

A glowing orange-to-red opal whose warm body color resembles flame; some stones add flashes of play-of-color.

A tourmaline displaying two or more distinct colors in a single crystal, prized for natural color zoning like watermelon and bicolor stones.

Australia's classic light-bodied precious opal from Coober Pedy, famed for milky white stones flashing pastel rainbow play-of-color.

A bronze-colored iron sulfide notable for being the most magnetic of the common sulfide minerals and an important nickel host.

A rare iron-rich (ferric) species of the tourmaline group, dark brown to bronze-black, named after crystallographer Martin Buerger.

A soft, reddish native metal with excellent conductivity, mined for wiring, plumbing, and alloys like bronze and brass.

Tourmaline displaying chatoyancy, a moving band of light caused by parallel tube-like inclusions, when cut as a cabochon.

A pale jasper threaded with black, fern-like mineral dendrites that mimic plants, trees, and frost despite being inorganic.

Purple-colored volcanic glass; genuine natural purple obsidian is rare, with much purple obsidian being manufactured colored glass.

Beryl displaying chatoyancy, a bright moving band of light, caused by parallel tube-like inclusions when cut as a cabochon.