Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Orendite
A rare ultrapotassic lamproite carrying sanidine, phlogopite and diopside, classically from Wyoming's Leucite Hills.
igneous
Herkimer Diamond
Exceptionally clear, naturally double-terminated quartz crystals from Herkimer County, New York, prized for their diamond-like brilliance.
crystal
Kersantite
A dark mica lamprophyre with biotite and augite phenocrysts in a plagioclase-dominated groundmass, the feldspar counterpart of minette.
igneous
Trachyte
A fine-grained volcanic rock dominated by alkali feldspar, the extrusive equivalent of syenite.
igneous
Phyllite
A fine-grained foliated metamorphic rock between slate and schist, recognized by its silky silvery sheen and wavy, crinkled surfaces.
metamorphic
Travertine
A banded, porous limestone deposited by mineral springs, prized as a warm-toned natural building and tile stone.
sedimentary
Needle Tourmaline
Fine acicular (needle-like) tourmaline crystals, often black schorl, frequently seen as slender inclusions within clear quartz.
mineral
Greenschist
A green, foliated low-grade metamorphic rock colored by chlorite, actinolite, and epidote, marking the greenschist metamorphic facies.
metamorphic
Topazolite Garnet
A rare yellow to golden variety of andradite garnet, the topaz-colored cousin of green demantoid, prized for high dispersion and brilliance.
gemstone
Cathedral Quartz
Quartz with a stepped, multi-pointed structure of parallel side crystals resembling the spires of a cathedral.
crystal
Black Opal
The rarest and most valuable opal, with a dark body tone that makes its flashing rainbow play-of-color blaze brilliantly.
gemstoneWyomingite
A rare ultrapotassic lamproite of leucite, phlogopite and diopside, named for and typified by Wyoming's Leucite Hills.
igneousRainbow Moonstone
A near-colorless feldspar showing blue and multicolored sheen; gemologically a white labradorite rather than true orthoclase moonstone.
gemstone
Yellow Tourmaline
Bright yellow to golden tourmaline colored by manganese, with the most vivid canary stones among the rarest tourmaline hues.
gemstone
Gabbro
A coarse-grained, dark mafic intrusive rock that is the plutonic equivalent of basalt, rich in plagioclase and pyroxene.
igneous
Rainbow Tourmaline
Tourmaline showing many color zones in a single crystal, often revealing spectacular concentric patterns when sliced.
gemstone
Petrified Wood
Ancient wood whose organic tissue has been replaced by silica, preserving the grain, rings, and structure of the original tree in stone.
sedimentary
Goethite
Goethite is a common brown iron oxyhydroxide, the main crystalline component of limonite and rust, with shimmering botryoidal forms.
mineral
Anorthoclase
A sodium-rich alkali feldspar of sodic volcanic rocks, sometimes forming large glassy crystals and the blue-flashing feldspar in larvikite.
mineral
Hemimorphite
A hydrous zinc silicate, often sky-blue, that is an ore of zinc and a collectible mineral forming botryoidal crusts and crystals.
mineral
Kakortokite
A spectacularly banded agpaitic nepheline syenite of alternating red eudialyte, black amphibole and white feldspar layers from Ilimaussaq, Greenland.
igneous
Marble
A metamorphosed limestone of interlocking calcite crystals, prized for sculpture and architecture for its workability and polish.
metamorphic
Plagioclase
The most abundant rock-forming feldspar group, a continuous solid-solution series from sodium albite to calcium anorthite that builds much of the crust.
mineral
Yttrium Aluminum Garnet
A synthetic garnet-structured oxide (YAG) used as a diamond simulant and laser crystal, with no natural counterpart.
gemstone