Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Rubicline
An extremely rare rubidium-dominant alkali feldspar, the rubidium analogue of microcline, found in rare-element granitic pegmatites.
mineral
Moonstone
A feldspar gem famous for adularescence, a floating blue-white glow that shimmers across the stone like moonlight.
gemstone
Carnotite
A bright yellow, radioactive potassium uranyl vanadate that is a major ore of both uranium and vanadium.
mineral
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
Sunstone
A feldspar gemstone that sparkles with metallic glints (aventurescence) caused by tiny reflective copper or hematite platelets.
gemstone
Slawsonite
A rare strontium-dominant feldspar, the strontium analogue of paracelsian, found in metamorphosed strontium-rich and manganese-bearing rocks.
mineral
Peach Moonstone
A warm peach-to-apricot variety of moonstone feldspar showing a soft billowy sheen (adularescence) caused by internal light scattering.
gemstone
Maskelynite
A natural glass formed when plagioclase feldspar is transformed by shock pressure during meteorite impacts, preserving crystal shape but losing crystal structure.
mineral
White Moonstone
The classic moonstone: a milky-white feldspar showing the prized floating blue-to-silver adularescent glow that gives the gem its name.
gemstone
Celsian
A rare barium-rich feldspar that forms in manganese and barium-enriched metamorphic and hydrothermal deposits, the barium end-member of the feldspar family.
mineral
Oligoclase
A sodium-rich plagioclase feldspar between albite and andesine, parent of aventurescent sunstone and the bluish gem peristerite.
mineral
Cat's Eye Moonstone
A moonstone variety displaying a moving band of light (chatoyancy) across its surface in addition to the classic moonstone glow.
gemstone
Reedmergnerite
A rare boron-bearing feldspar, the boron analogue of albite, first found in oil-shale nodules of the Green River Formation.
mineral
Labradorite
A plagioclase feldspar famous for labradorescence, a dramatic flash of iridescent blue, green, and gold across a dark gray stone.
mineral
Green Moonstone
A pale green variety of feldspar moonstone showing a soft white or bluish adularescent sheen over a greenish body.
gemstone
Banalsite
A rare barium-sodium aluminosilicate of the feldspar group, found chiefly in metamorphosed manganese ore deposits.
mineral
Andesine
An intermediate plagioclase feldspar between albite and anorthite, marketed as a red to champagne gemstone, sometimes color-treated.
gemstone
Grey Moonstone
A smoky gray feldspar moonstone, often called new moon stone, showing a silvery-blue adularescent sheen over a translucent gray body.
gemstone
Paracelsian
A rare barium aluminosilicate that is a monoclinic polymorph of celsian, found in barium-rich metamorphic and manganese deposits.
mineral
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.
gemstone
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
Graphic Granite
A pegmatitic granite in which quartz and feldspar intergrow to resemble ancient runic or Hebrew script.
igneous