Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Chrysocolla
A vivid blue-green hydrated copper silicate, soft on its own but prized as a gem when hardened by intergrown quartz or chalcedony.
mineralCopper
A soft, reddish native metal with excellent conductivity, mined for wiring, plumbing, and alloys like bronze and brass.
mineral
Aquamarine Matrix
Aquamarine crystals still attached to their natural host rock, prized as mineral specimens showing beryl in its original pocket setting.
mineral
Emerald in Matrix
Natural emerald crystals still embedded in their host rock, prized as mineral specimens that show how the gem grew in place.
gemstone
Matrix Opal
Opal in which precious play-of-color is intimately dispersed through the pores of its host rock rather than forming a solid seam.
gemstone
Peacock Ore
A copper-iron sulfide ore famous for its iridescent peacock-like purple and blue tarnish; often sold as treated chalcopyrite.
mineral
Copper-Bearing Tourmaline
Tourmaline colored by copper, producing the famous vivid neon blues, greens and teals known commercially as Paraiba-type gems.
gemstone
Gem Silica
A rare, intensely blue chalcedony colored by copper-rich chrysocolla, prized as the most valuable of the blue chalcedonies.
gemstone
Chalcopyrite
A brassy copper-iron sulfide that is the world's most important copper ore, often showing colorful iridescent tarnish.
mineral
Bornite
A copper iron sulfide famous for its vivid iridescent purple-blue tarnish, the classic peacock ore and a copper ore.
mineral
Cuprite
Cuprite is a deep red copper oxide and an important secondary copper ore, prized for its rare ruby-red gem crystals.
mineral
Chalcocite
A dark gray copper sulfide that is one of the richest copper ores, prized by collectors when found as rare sharp crystals.
mineralSonoran Sunset Jasper
A vivid copper-bearing Mexican stone of red cuprite and green chrysocolla that evokes a desert sunset.
mineral
Shattuckite
A rare deep-blue copper silicate mineral, often fibrous or massive, named for the Shattuck Mine in Arizona and prized by collectors.
mineral
Malachite
A vivid green copper carbonate mineral famous for swirling concentric bands, used as an ore of copper and an ornamental gemstone.
mineral
Tetrahedrite
A gray copper-antimony sulfosalt of the fahlore group, an important ore of copper and often silver, forming tetrahedral crystals.
mineral
Azurite
A deep blue copper carbonate mineral that forms in oxidized copper deposits, often alongside green malachite.
mineral
Niccolite
A pale copper-red nickel arsenide, historically called kupfernickel, that is an ore of nickel and gives the metal its name.
mineral
Honduran Opal
Precious opal from Honduras occurring in a dark volcanic matrix, where bright flecks of color flash against a natural black basalt background.
gemstone
Banded Iron Formation
Ancient chemically deposited rock of alternating iron-oxide and silica bands recording Earth's early oxygenation and a major iron ore source.
sedimentary
Covellite
A soft copper sulfide famous for its intense indigo-blue color and dazzling iridescent metallic sheen, prized by collectors.
mineral
Bog Iron
A soft, porous iron ore of limonite and goethite that forms in wetlands and bogs, historically the first iron source for many cultures.
sedimentary
Boulder Opal
Precious opal that forms in thin veins within brown ironstone boulders, cut with the host rock left as a natural dark backing.
gemstone
Andamooka Opal
Precious opal from the Andamooka field of South Australia, famous for solid crystal opal and its distinctive treatable matrix opal.
gemstone