Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Obsidian
A glassy, jet-black volcanic rock formed when lava cools too fast to crystallize, prized for razor-sharp conchoidal edges.
igneous
Black Obsidian
Jet-black natural volcanic glass formed by rapidly cooled lava, prized for its glassy luster and razor-sharp conchoidal fracture.
igneousMacusanite
A rare translucent yellow-green volcanic glass from the Macusani region of Peru, valued by faceters and sometimes confused with tektites.
igneous
Baddeleyite
A natural zirconium dioxide mineral, hard and refractory, valued as a zirconium source and prized for high-precision U-Pb dating.
mineral
Green Obsidian
Green-tinted volcanic glass; some is naturally colored by trace iron, but vivid emerald-green pieces are usually manufactured glass.
crystalBlue Obsidian
Blue-colored volcanic glass; genuine natural blue obsidian is very rare, while much blue obsidian on the market is manufactured glass.
crystal
Maskelynite
A natural glass formed when plagioclase feldspar is transformed by shock pressure during meteorite impacts, preserving crystal shape but losing crystal structure.
mineralMidnight Obsidian
A trade name for deep, solid black obsidian, natural volcanic glass prized for its uniform jet-black color and glassy luster.
igneous
Sideromelane
A transparent, pale brown basaltic volcanic glass formed when basalt lava is quenched extremely fast, often underwater.
igneous
Yellow-Green Obsidian
A chartreuse yellow-green glass sold as obsidian; the bright color is manufactured and does not occur in natural volcanic glass.
igneousPink Obsidian
A pink to rose volcanic glass; some is natural iron-tinted obsidian while much sold commercially is color-treated glass.
igneous
Perlite
A hydrated volcanic glass with pearly, onion-like concentric cracks that pops into lightweight white granules when heated.
igneous
Tachylite
An opaque, iron-rich basaltic volcanic glass formed by the rapid chilling of basalt lava, darker and denser than rhyolitic obsidian.
igneousTeal Obsidian
A deep teal glass sold as obsidian; the saturated blue-green color is manufactured and not found in natural volcanic glass.
igneousCobalt Blue Obsidian
A deep cobalt-blue glass sold as obsidian; intense blue body color is manufactured, as natural obsidian does not form bright blue glass.
igneous
Purple Obsidian
Purple-colored volcanic glass; genuine natural purple obsidian is rare, with much purple obsidian being manufactured colored glass.
crystalTurquoise Obsidian
A vivid turquoise-blue glass sold as obsidian; this bright color is virtually always manufactured rather than natural volcanic glass.
igneous
Halite
The natural mineral form of table salt, a soft, water-soluble evaporite that forms perfect cubic crystals and tastes salty.
mineral
Porphyritic Obsidian
Natural volcanic glass speckled with embedded mineral crystals (phenocrysts) such as feldspar or cristobalite that grew before the lava chilled.
igneous
Hyalite Opal
A clear, glassy, botryoidal common opal famous for its intense green fluorescence under UV light, caused by trace uranium.
gemstoneViolet Obsidian
A violet-to-purple glass sold as obsidian; uniform purple material is almost always manufactured glass rather than natural volcanic obsidian.
igneous
Opalite
A man-made opalescent glass that glows milky blue in reflected light and warm orange when backlit, often sold as a crystal.
crystal
Goldstone
A man-made glittering glass packed with tiny copper crystals, traditionally reddish-brown but also made in blue and green.
crystal
Yellow Obsidian
Yellow to golden volcanic glass; natural examples owe their color to iron, though much bright yellow obsidian on the market is manufactured glass.
igneous