Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Silcrete
Extremely hard surface rock formed when silica cements soil and sediment into a tough duricrust in arid landscapes.
sedimentary
Ruby
The red, chromium-colored variety of corundum, prized as one of the most valuable colored gemstones and second only to diamond in hardness.
gemstone
Reptile Jasper
A green-and-black mottled jasper whose scale-like patterning resembles reptile skin, often linked to Kambaba and crocodile jaspers.
mineral
Rhodolite Garnet
A purplish-red to raspberry garnet that is a natural blend of pyrope and almandine, prized for its bright rose-violet color.
gemstone
Pink Beryl
The pink to peach variety of beryl, better known as morganite, colored by manganese and prized for its gentle pastel hues.
gemstone
Owyhee Jasper
A picture jasper from the Owyhee region of Oregon and Idaho, prized for scenic tan, cream, and blue-grey landscape patterns.
mineral
Orange Garnet
A trade term for orange garnets, mainly manganese-rich spessartine and the brownish hessonite variety of grossular.
gemstone
Orange Calcite
A soft, glowing orange variety of calcite colored by iron oxides, popular as tumbled stones and known for fizzing in acid.
mineral
Mookaite
A vivid Australian jasper-like silica stone in earthy reds, yellows, and purples, formed from silicified radiolarian sediment.
mineral
Mintabie Opal
Precious opal from the Mintabie field in South Australia, known for hard, bright crystal opal and some dark-bodied stones.
gemstone
Micrite
A very fine-grained limestone made of microcrystalline calcite mud, dense and smooth, deposited in calm carbonate settings.
sedimentary
Masasi Blue Garnet
Masasi Blue Garnet is a rare vanadium-bearing color-change garnet from Tanzania that appears blue-green by day and purplish-red indoors.
gemstone
Magnesite
A magnesium carbonate mineral, usually chalky white with grey veining, widely dyed to imitate turquoise and other stones.
mineral
London Blue Topaz
The deepest, most saturated blue grade of treated topaz, prized for its rich steely-blue color and durability in jewelry.
gemstone
Labradorite
A plagioclase feldspar famous for labradorescence, a dramatic flash of iridescent blue, green, and gold across a dark gray stone.
mineral
Heliodor
The golden-yellow gem variety of beryl, colored by iron, prized for its bright sunshine hue and excellent durability.
gemstone
Gypsum
A very soft sulfate mineral defining Mohs 2, occurring as selenite, satin spar, alabaster, and desert rose, used to make plaster.
mineral
Hot Pink Tourmaline
An intensely saturated hot-pink to magenta elbaite tourmaline, among the most vivid and eye-catching of all pink rubellites.
gemstone
Goldmanite
A green, vanadium-dominant garnet that forms in vanadium-rich metamorphic and sedimentary rocks, notably in uranium-vanadium districts.
mineral
Geyserite
Porous opaline silica deposited around geysers and hot springs, often preserving delicate microbial textures.
sedimentary
Gneiss
A high-grade metamorphic rock defined by alternating light and dark mineral bands, formed under intense heat and pressure.
metamorphic
Gabbro
A coarse-grained, dark mafic intrusive rock that is the plutonic equivalent of basalt, rich in plagioclase and pyroxene.
igneous
Fancy Jasper
A soft-toned, multicolored jasper with swirling green, mauve, and cream patterns, popular and affordable in the bead trade.
sedimentary
Euxenite
A black rare-earth niobium-tantalum oxide, often radioactive and metamict, mined for yttrium, niobium, and associated rare elements.
mineral