Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Amethyst
The purple variety of quartz, colored by iron and natural irradiation, prized as the classic violet birthstone of February.
crystalStar Moonstone
A rare moonstone that shows a four-rayed star of light (asterism) across its domed surface along with adularescence.
gemstone
Star Aquamarine
A rare blue beryl that shows asterism, a moving star of light from intersecting sets of parallel inclusions, when cut as a cabochon.
gemstone
Chevron Amethyst
A naturally banded quartz combining purple amethyst and white quartz in striking V-shaped chevron or zigzag patterns.
crystal
Brandberg Amethyst
A prized Namibian quartz combining amethyst, smoky, and clear quartz in single crystals, often with phantoms and enhydros.
crystal
Star Opal
Opal that displays a radiating, star-shaped pattern of play-of-color, a rare and prized internal structure.
gemstone
Star Garnet
A rare almandine garnet that displays a four- or six-rayed star (asterism) from oriented rutile inclusions; the state gem of Idaho.
gemstone
Star Rose Quartz
Rose quartz that displays a six-rayed star (asterism) when cut as a cabochon, caused by microscopic rutile-like inclusions.
gemstone
Idaho Star Garnet
Idaho's official state gem: a dark almandine garnet showing a four- or rare six-rayed star from oriented rutile inclusions.
gemstoneAmegreen
A natural bicolor quartz blending amethyst purple with prasiolite green in a single crystal, prized as a metaphysical heart-crown stone.
crystal
Prasiolite
A pale green variety of quartz, usually created by heat-treating amethyst, often marketed as green amethyst.
gemstoneStarburst Agate
Agate containing radiating sprays of mineral needles that fan out like bursting stars within the chalcedony.
gemstone
Cactus Quartz
A South African quartz whose central crystal is coated in a cactus-like crust of tiny secondary points, also called spirit quartz.
crystal
Green Quartz
A green variety of macrocrystalline quartz, usually the heat- or radiation-altered prasiolite, prized for its soft mint hue.
crystal
Ametrine
A natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.
crystalTrapiche Aquamarine
A rare blue beryl showing a fixed six-spoke wheel pattern caused by impurity inclusions arranged along the crystal's growth axis.
gemstone
Trapiche Tourmaline
A rare tourmaline showing a fixed wheel-like pattern of color zones and arms radiating from the crystal's center.
gemstone
Grape Agate
Clusters of tiny botryoidal chalcedony spheres resembling bunches of grapes, famously purple, found in Indonesia.
mineral
Spirit Quartz
A South African quartz whose central crystal is coated in tiny druzy points, also called cactus or fairy quartz.
crystal
Sapphire
The gem variety of corundum in every color except red, most prized in velvety blue and exceptionally hard and durable.
gemstone
Trapiche Emerald
A rare emerald showing a six-spoked star pattern of dark inclusions, named after the spokes of a sugar-mill wheel.
gemstoneCandle Quartz
A quartz with a main point surrounded by many smaller crystals along its sides, resembling melted candle wax, mainly from Madagascar.
crystal
Purple Obsidian
Purple-colored volcanic glass; genuine natural purple obsidian is rare, with much purple obsidian being manufactured colored glass.
crystal
Kunzite
The delicate pink-to-lilac variety of spodumene, a lithium silicate prized for soft color and strong pleochroism but tricky perfect cleavage.
gemstone