Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
London Blue Topaz
The deepest, most saturated blue grade of treated topaz, prized for its rich steely-blue color and durability in jewelry.
gemstone
Mica
A family of sheet silicate minerals that split into thin, flexible, shiny sheets, giving rocks a sparkling, layered appearance.
mineral
Labradorite
A plagioclase feldspar famous for labradorescence, a dramatic flash of iridescent blue, green, and gold across a dark gray stone.
mineral
Garnet
A group of silicate gemstones best known for deep red but spanning nearly every color, including green tsavorite and orange spessartine.
gemstone
Tillite
A lithified glacial till, a poorly sorted rock of mixed boulders, pebbles and fine matrix that records ancient glaciations.
sedimentary
Rainbow Tourmaline
Tourmaline showing many color zones in a single crystal, often revealing spectacular concentric patterns when sliced.
gemstone
Lignite
The lowest rank of coal, a soft brown carbon-rich rock formed from compacted peat, used mainly for electricity generation.
sedimentary
Welo Opal
Bright play-of-color opal from the Wollo Province of Ethiopia, mostly hydrophane and known for broad, vivid fire.
gemstone
Vanadinite
A brilliant orange-red lead vanadate mineral forming hexagonal crystals, prized by collectors and mined as an ore of vanadium.
mineral
Troctolite
A mafic plutonic rock of plagioclase and olivine whose mottled appearance earned it the nickname 'troutstone'.
igneous
Tantalite
A dense black iron-manganese tantalate that is the chief ore of tantalum, forming a series with columbite and mined as coltan.
mineral
Siderite
Siderite is an iron carbonate ore, a brown rhombohedral mineral of the calcite group found in sediments and veins.
mineral
Pyrrhotite
A bronze-colored iron sulfide notable for being the most magnetic of the common sulfide minerals and an important nickel host.
mineral
Malachite
A vivid green copper carbonate mineral famous for swirling concentric bands, used as an ore of copper and an ornamental gemstone.
mineral
Limestone
A soft carbonate sedimentary rock made mostly of calcite, often packed with marine fossils and prone to forming caves.
sedimentary
Kimberlite
A rare ultramafic volcanic rock that erupts from deep in the mantle and is the primary natural source of diamonds.
igneous
Calc-schist
A foliated metamorphic rock of calcite mixed with mica, quartz, and calc-silicate minerals, derived from marly sediments.
metamorphic
Raspberry Beryl
A trade name for raspberry-pink beryl-family gems, most often the cesium-rich mineral pezzottaite from Madagascar.
gemstone
Peat
A soft, spongy accumulation of partly decayed plant matter that forms in waterlogged bogs and is the first step toward coal.
sedimentary
Dumortierite Quartz
Quartz colored blue by inclusions of the mineral dumortierite, giving a denim-like blue ornamental stone harder than dumortierite alone.
gemstone
Melteigite
A dark, pyroxene-dominated plutonic rock at the mafic end of the ijolite series, made mainly of aegirine-augite with subordinate nepheline.
igneous
Dark Green Tourmaline
Deeply saturated green tourmaline colored by iron, often so dark it appears nearly black until viewed in bright light.
gemstone
Spectrolite
A premium dark Finnish labradorite displaying the full color spectrum of iridescent flashes, prized as one of the most vivid feldspar gems.
gemstone
Jelly Opal
A translucent, gelatinous-looking opal whose transparency gives floating, glowing play-of-color a watery, jelly-like appearance.
gemstone