Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Katoite
The water-rich end-member of the hydrogrossular series, a soft hydrogarnet found in altered rocks and known from cement chemistry.
mineral
Feldspar
The most abundant mineral group in Earth's crust, feldspars are aluminosilicates that form much of granite and many igneous rocks.
mineral
Mookaite
A vivid Australian jasper-like silica stone in earthy reds, yellows, and purples, formed from silicified radiolarian sediment.
mineral
Slate
A fine-grained, low-grade metamorphic rock that splits into flat sheets along slaty cleavage, long used for roofing and flooring.
metamorphic
Opalite
A man-made opalescent glass that glows milky blue in reflected light and warm orange when backlit, often sold as a crystal.
crystal
Jacupirangite
A rare dark ultramafic alkaline igneous rock built mostly of titanaugite and magnetite, named for Jacupiranga in Brazil.
igneous
Orange Calcite
A soft, glowing orange variety of calcite colored by iron oxides, popular as tumbled stones and known for fizzing in acid.
mineral
Gneiss
A high-grade metamorphic rock defined by alternating light and dark mineral bands, formed under intense heat and pressure.
metamorphic
Black Onyx
A solid jet-black chalcedony, usually a dyed and treated agate, prized for sleek polished beads, cabochons, and intaglios.
gemstone
Snakeskin Jasper
An opaque patterned jasper named for its scaly, snakeskin-like surface markings of interlocking tan and brown cells.
mineral
Calcarenite
Sand-grained limestone composed of carbonate particles such as shell fragments and ooids cemented into a calcite rock.
sedimentary
Slawsonite
A rare strontium-dominant feldspar, the strontium analogue of paracelsian, found in metamorphosed strontium-rich and manganese-bearing rocks.
mineral
Orthoclase
A common rock-forming potassium feldspar, the Mohs hardness reference at 6, found in granites and used in ceramics and glassmaking.
mineral
Deschutes Jasper
A prized Oregon picture jasper from the Deschutes region known for soft scenic landscapes in cream, tan, and blue-gray.
mineral
Glauconite
A soft, green iron-potassium mica that forms in marine sediments and gives greensand its characteristic olive color.
mineral
Rose Tourmaline
A soft to medium pink elbaite tourmaline in rose hues, colored by manganese and prized for romantic jewelry.
gemstone
Shattuckite
A rare deep-blue copper silicate mineral, often fibrous or massive, named for the Shattuck Mine in Arizona and prized by collectors.
mineral
Paracelsian
A rare barium aluminosilicate that is a monoclinic polymorph of celsian, found in barium-rich metamorphic and manganese deposits.
mineral
Sapphire
The gem variety of corundum in every color except red, most prized in velvety blue and exceptionally hard and durable.
gemstone
Nephrite
One of the two jade minerals, an amphibole prized for its extreme toughness and soft, waxy green hues used in carving for millennia.
gemstone
Green Opal
A common opal colored green by nickel or chromium impurities, usually opaque and cut into cabochons and beads.
gemstone
Fire Opal
A translucent to transparent opal in warm yellow, orange, and red tones, prized for body color rather than play-of-color.
gemstone
Carrasite Jasper
An orbicular Madagascar jasper related to ocean jasper, showing eyes and swirls in cream, green, and earthy tones.
mineral
Feruvite
A calcium- and ferrous-iron-rich tourmaline, the iron analogue of uvite, forming dark brown to black crystals in skarns and metamorphic rocks.
mineral