Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Crocoite
A striking lead chromate mineral prized for its brilliant orange-red prismatic crystals, with the finest specimens from Tasmania.
mineral
Clear Obsidian
An unusually pure, transparent-to-translucent obsidian with few inclusions; truly water-clear specimens are rare in nature.
igneous
Goldstone
A man-made glittering glass packed with tiny copper crystals, traditionally reddish-brown but also made in blue and green.
crystal
Tillite
A lithified glacial till, a poorly sorted rock of mixed boulders, pebbles and fine matrix that records ancient glaciations.
sedimentary
Calc-schist
A foliated metamorphic rock of calcite mixed with mica, quartz, and calc-silicate minerals, derived from marly sediments.
metamorphic
Magnetite
A naturally magnetic black iron oxide and a major iron ore; strongly magnetic specimens are known as lodestone.
mineral
Calc-Silicate Rock
A metamorphic rock of calcium-rich silicate minerals formed from impure limestone or dolomite altered by heat and fluids.
metamorphic
Granulite
A high-grade metamorphic rock formed in the deep, hot crust, marked by anhydrous minerals like pyroxene and garnet.
metamorphic
Maskelynite
A natural glass formed when plagioclase feldspar is transformed by shock pressure during meteorite impacts, preserving crystal shape but losing crystal structure.
mineral
Ametrine
A natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.
crystal
Orange Tourmaline
A warm orange to tangerine tourmaline, an uncommon hue produced by manganese and iron in the crystal.
gemstone
Schorl
The common iron-rich black variety of tourmaline, by far the most abundant tourmaline species and a popular grounding crystal.
mineralTri-Color Tourmaline
Tourmaline displaying three distinct color zones in a single crystal, a striking natural result of changing growth chemistry.
gemstone
Rainbow Tourmaline
Tourmaline showing many color zones in a single crystal, often revealing spectacular concentric patterns when sliced.
gemstone
Celestite
A soft, sky-blue strontium sulfate mineral famous for the glittering pale-blue crystal geodes from Madagascar.
mineralAmegreen
A natural bicolor quartz blending amethyst purple with prasiolite green in a single crystal, prized as a metaphysical heart-crown stone.
crystal
Bi-Color Tourmaline
Tourmaline displaying two distinct colors in a single crystal, a natural color-zoning effect that makes each stone unique.
gemstone
Watermelon Tourmaline
A striking color-zoned tourmaline with a pink center and green rind, resembling a slice of watermelon when cut across the crystal.
gemstone
Tourmaline
A boron-rich silicate gemstone group famous for occurring in every color of the rainbow, sometimes several within a single crystal.
gemstone
Australian Opal
Opal from Australia, the world's leading source of precious opal, ranging from white and crystal to prized black and boulder types.
gemstoneParticolored Tourmaline
A tourmaline displaying two or more distinct colors in a single crystal, prized for natural color zoning like watermelon and bicolor stones.
gemstone
Foitite
A rare alkali-deficient tourmaline whose X crystal site is largely vacant, giving slender dark blue to bluish-black crystals.
mineral
Bi-color Beryl
A single beryl crystal showing two distinct color zones, such as aquamarine blue grading into morganite pink, within one stone.
gemstone
Opalite
A man-made opalescent glass that glows milky blue in reflected light and warm orange when backlit, often sold as a crystal.
crystal