Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Reedmergnerite
A rare boron-bearing feldspar, the boron analogue of albite, first found in oil-shale nodules of the Green River Formation.
mineralNordmarkite
A light-colored alkali quartz syenite dominated by perthitic feldspar with minor quartz, from the Oslo igneous province of Norway.
igneous
Labradorite
A plagioclase feldspar famous for labradorescence, a dramatic flash of iridescent blue, green, and gold across a dark gray stone.
mineral
Andesine
An intermediate plagioclase feldspar between albite and anorthite, marketed as a red to champagne gemstone, sometimes color-treated.
gemstoneBanalsite
A rare barium-sodium aluminosilicate of the feldspar group, found chiefly in metamorphosed manganese ore deposits.
mineral
Paracelsian
A rare barium aluminosilicate that is a monoclinic polymorph of celsian, found in barium-rich metamorphic and manganese deposits.
mineral
Latite
The fine-grained volcanic equivalent of monzonite, an intermediate lava with nearly equal feldspars and little free quartz.
igneous
Andesine-Labradorite
An intermediate plagioclase feldspar spanning andesine and labradorite, marketed as a red-to-green gem, much of which is copper-diffusion treated.
gemstone
Bytownite
A calcium-rich plagioclase feldspar between labradorite and anorthite, faceted as transparent golden-yellow gems sometimes sold as yellow labradorite.
gemstonePrase
An old name for a dull leek-green variety of quartz or chalcedony colored by green mineral inclusions, historically called mother of emerald.
crystal
Oregon Sunstone
A copper-bearing labradorite feldspar from Oregon, famous for its range of natural colors and glittery aventurescent copper schiller.
gemstone
Peristerite
A sodium-rich plagioclase moonstone whose fine intergrowth lamellae scatter light into a delicate blue, pigeon-neck sheen.
gemstone
Chalcedony
A waxy, translucent microcrystalline form of quartz that serves as the parent group for agate, jasper, carnelian, and onyx.
mineral
Ametrine
A natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.
crystal
Citrine
The golden-yellow variety of quartz, ranging from pale lemon to deep madeira amber, often produced by heating amethyst.
gemstone
Tonalite
A quartz-rich plutonic rock dominated by plagioclase feldspar with little alkali feldspar, closely related to granodiorite and quartz diorite.
igneous
Herkimer Diamond
Exceptionally clear, naturally double-terminated quartz crystals from Herkimer County, New York, prized for their diamond-like brilliance.
crystal
Amethyst
The purple variety of quartz, colored by iron and natural irradiation, prized as the classic violet birthstone of February.
crystal
Arkose
A coarse, feldspar-rich sandstone, often pink, that records rapid erosion of granitic source rock under arid conditions.
sedimentaryAmegreen
A natural bicolor quartz blending amethyst purple with prasiolite green in a single crystal, prized as a metaphysical heart-crown stone.
crystal
Tiger's Eye
A golden-brown chatoyant quartz with a shimmering silky band of light, formed when quartz replaces fibrous crocidolite.
gemstone
Monzonite
An intermediate plutonic rock with nearly equal alkali and plagioclase feldspar and very little quartz, sitting between diorite and syenite.
igneousKiwi Jasper
A speckled green-and-black stone resembling kiwi fruit, technically a quartz-amazonite aggregate rather than true jasper.
mineral
Unakite
An altered granite mottled pink and green from feldspar and epidote, popular as a tough, colorful ornamental rock.
metamorphic