Rock & Mineral Encyclopedia

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

Reedmergnerite

A rare boron-bearing feldspar, the boron analogue of albite, first found in oil-shale nodules of the Green River Formation.

Iron-stained sandstone whose red color comes from hematite coatings, formed in oxidizing desert, river, and coastal environments.

Glacially transported banded agates found along Lake Huron's shores, typically small, frosted pebbles with red-orange iron banding.

Limestone built from tiny rounded ooid grains resembling fish roe, formed in warm, agitated shallow seas.

A rare agate that forms naturally with flat polygonal faces and angular geometric shapes rather than the usual rounded nodule.

Black volcanic glass crossed by a fine network of grey or brown veins that resemble a spider's web.

A mottled, multicolored obsidian blending black, brown, grey, and tan patches like a calico cat's patchwork coat.

A classic Oregon picture jasper showing layered tan, brown, and blue-grey scenes resembling desert landscapes and canyons.

An opaque grey-brown common opal forming nodules and concretions, historically called liver opal for its dull brownish color.