Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Sulfur
A bright yellow native element mineral that forms around volcanic vents and hot springs and burns with a blue flame.
mineral
Blue Apatite
A blue calcium phosphate mineral with vivid color and middling hardness, the same mineral family that forms bones and teeth.
mineral
Amethyst
The purple variety of quartz, colored by iron and natural irradiation, prized as the classic violet birthstone of February.
crystal
Chevron Amethyst
A naturally banded quartz combining purple amethyst and white quartz in striking V-shaped chevron or zigzag patterns.
crystal
Purple Obsidian
Purple-colored volcanic glass; genuine natural purple obsidian is rare, with much purple obsidian being manufactured colored glass.
crystal
Purple Agate
A purple-toned banded chalcedony, sometimes naturally amethystine but frequently produced by dyeing gray agate.
gemstone
Purple Tourmaline
An uncommon purple to violet tourmaline colored by manganese, the deeper reddish-purple stones sometimes called siberite.
gemstone
Purple Opal
A purple-hued common opal, much of it the Mexican "morado" type, valued for even violet color rather than play-of-color.
gemstone
Purple Sheen Obsidian
Black volcanic glass that reveals a soft purple-to-violet sheen at certain angles, caused by light interference off aligned inclusions.
igneous
Holley Blue Agate
A rare translucent lavender-blue agate from the Holley area of Oregon, prized for its soft purple-blue color.
gemstone
Ametrine
A natural bicolor quartz that combines purple amethyst and golden citrine in a single crystal.
crystal
Amegreen
A natural bicolor quartz blending amethyst purple with prasiolite green in a single crystal, prized as a metaphysical heart-crown stone.
crystal
Grape Agate
Clusters of tiny botryoidal chalcedony spheres resembling bunches of grapes, famously purple, found in Indonesia.
mineral
Violet Obsidian
A violet-to-purple glass sold as obsidian; uniform purple material is almost always manufactured glass rather than natural volcanic obsidian.
igneous
Citrine
The golden-yellow variety of quartz, ranging from pale lemon to deep madeira amber, often produced by heating amethyst.
gemstone
Kimberlite
A rare ultramafic volcanic rock that erupts from deep in the mantle and is the primary natural source of diamonds.
igneous
Bumblebee Jasper
A vivid yellow-and-black banded stone from Indonesian volcanic vents, colored by sulfur, arsenic minerals and iron oxides, not true jasper.
sedimentary
Goldstone
A man-made glittering glass packed with tiny copper crystals, traditionally reddish-brown but also made in blue and green.
crystal
Plum Tourmaline
A purplish, plum-toned elbaite tourmaline colored by manganese, blending the red of rubellite with violet-blue undertones.
gemstone
Bornite
A copper iron sulfide famous for its vivid iridescent purple-blue tarnish, the classic peacock ore and a copper ore.
mineral
Peacock Ore
A copper-iron sulfide ore famous for its iridescent peacock-like purple and blue tarnish; often sold as treated chalcopyrite.
mineral
Lindi Garnet
Lindi Garnet is a rare vanadium-rich color-change garnet from Tanzania's Lindi region, shifting from blue-green daylight tones to purple-red.
gemstone
Mookaite
A vivid Australian jasper-like silica stone in earthy reds, yellows, and purples, formed from silicified radiolarian sediment.
mineral
Smithsonite
Smithsonite is a zinc carbonate ore famous for glassy botryoidal crusts in blue-green, pink, and yellow hues.
mineral