Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Andalusite
A pleochroic aluminum silicate that flashes green and reddish-brown from different angles, with a cross-marked variety called chiastolite.
mineral
Staurolite-mica Schist
A mica schist studded with red-brown staurolite porphyroblasts, including the famous cross-shaped twins called fairy stones.
metamorphic
Staurolite Schist
A mica schist studded with brown staurolite porphyroblasts, sometimes forming the cross-shaped twins known as fairy stones.
metamorphic
Faden Quartz
Tabular quartz crossed by a milky white thread-like line marking where the crystal repeatedly cracked and re-healed.
crystalSpiderweb Jasper
A jasper crossed by fine dark veins forming a spiderweb-like network, often a brecciated stone cemented by darker matrix.
mineralSpiderweb Obsidian
Black volcanic glass crossed by a fine network of grey or brown veins that resemble a spider's web.
igneousBlue Line Jasper
A pale jasper crossed by distinctive blue-gray veins or lines, valued by lapidaries for its calm color contrast.
gemstoneStripe Obsidian
Obsidian crossed by parallel flow bands of differing color, formed as layers of lava with slightly different compositions froze into glass.
igneous
Liddicoatite
A rare calcium-rich lithium tourmaline famous for the spectacular concentric color zoning seen in polished cross-section slices.
mineral
Pineapple Opal
A rare opal pseudomorph from White Cliffs, Australia, formed as opal replaced clustered crystals into a pineapple-like shape.
gemstoneCat's Eye Opal
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.
gemstone
Leopard Opal
A patterned common opal with mottled, leopard-like spots and blotches, prized as an ornamental and cabochon stone.
gemstone
Dendritic Opal
A common opal with branching, tree-like mineral inclusions that create natural fern, moss, or landscape patterns.
gemstone
Water Opal
A transparent, colorless opal that looks like water or jelly, sometimes flashing subtle play-of-color from within.
gemstone
Moss Opal
A common opal containing moss- or fern-like mineral inclusions that resemble plants suspended in a pale silica body.
gemstoneSatin Opal
Opal showing a smooth, silky satin-like sheen across its surface, valued for a gentle, refined luster.
gemstone
Landscape Opal
A common opal containing dendritic or mossy mineral inclusions that form miniature landscape-like scenes inside the stone.
gemstone
Peacock Opal
A precious opal showing dominant peacock-like blue, green and teal play-of-color, often on Ethiopian material.
gemstone
Jelly Opal
A translucent, gelatinous-looking opal whose transparency gives floating, glowing play-of-color a watery, jelly-like appearance.
gemstone
Cacholong Opal
An opaque, porcelain-white common opal prized for its milky, pearl-like appearance and high porosity, often carved or beaded.
gemstone
Pinfire Opal
A precious opal pattern made of tiny, densely packed pinpoint flashes of play-of-color, like sparkling speckles across the stone.
gemstoneMilk Opal
An opaque to translucent milky-white common opal valued for its soft porcelain-like color rather than play-of-color.
gemstone