Rock & Mineral Encyclopedia

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

Millerite

A nickel sulfide famous for delicate brass-yellow hairlike crystals that form radiating sprays inside cavities and geodes.

A rare translucent yellow-green volcanic glass from the Macusani region of Peru, valued by faceters and sometimes confused with tektites.

A vivid Australian jasper-like silica stone in earthy reds, yellows, and purples, formed from silicified radiolarian sediment.

A rounded sedimentary nodule cracked internally and filled with veins of yellow calcite, prized for its striking dragon-skin patterning.

A multicolored orbicular chalcedony from Madagascar famous for its circular eye-like orbs in greens, pinks, whites, and yellows.

A translucent to transparent opal in warm yellow, orange, and red tones, prized for body color rather than play-of-color.

A yellow-brown alteration material formed when basaltic volcanic glass reacts with water, common in hydrovolcanic tuffs and pillow lavas.

A translucent yellow-green silicate famous for its botryoidal 'grape' clusters, often hosting needle-like sprays of black epidote.

An opal cut to show chatoyancy, a sharp moving band of light like a cat's eye, usually in honey, green or yellow common opal.

A hard zinc-rich member of the spinel group, usually dark blue-green to black, forming octahedral crystals in metamorphic and pegmatitic rocks.