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.
mineral
Gem Silica
A rare, intensely blue chalcedony colored by copper-rich chrysocolla, prized as the most valuable of the blue chalcedonies.
gemstone
Chalcedony
A waxy, translucent microcrystalline form of quartz that serves as the parent group for agate, jasper, carnelian, and onyx.
mineral
Blue Chalcedony
A translucent, soft blue variety of microcrystalline quartz whose color comes from light scattering through its fine structure.
mineral
Chrome Chalcedony
A vivid green chalcedony colored by chromium, often called mtorolite, resembling chrysoprase but owing its color to chromium rather than nickel.
gemstoneSonoran 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
Black Jasper
A dense, opaque black variety of microcrystalline quartz historically used as a touchstone for testing precious metals.
mineral
Blue Jasper
An opaque blue variety of chalcedony jasper, less common than red or green forms, colored by mineral inclusions.
mineral
Green Jasper
An opaque green variety of chalcedony quartz colored by iron and chlorite-group inclusions, prized as a durable carving and cabochon stone.
mineral
Precious Opal
The classic gem opal that flashes shifting spectral colors, defined by the diffraction effect known as play-of-color.
gemstone
Brecciated Agate
Agate that was shattered and naturally re-cemented by silica, creating a mosaic of angular fragments in a quartz matrix.
gemstone
Chrysoprase
A translucent apple-green chalcedony colored by nickel, the most prized green variety of the quartz family.
gemstoneSard
A brownish-red to deep brown variety of chalcedony, closely related to carnelian but darker, colored by iron oxides.
mineral
Geyserite
Porous opaline silica deposited around geysers and hot springs, often preserving delicate microbial textures.
sedimentary
Black Opal
The rarest and most valuable opal, with a dark body tone that makes its flashing rainbow play-of-color blaze brilliantly.
gemstone
Crystal Opal
Precious opal with a transparent or translucent body, letting play-of-color glow with exceptional depth and clarity.
gemstone
Grape Agate
Clusters of tiny botryoidal chalcedony spheres resembling bunches of grapes, famously purple, found in Indonesia.
mineral
Elbaite
The lithium-rich tourmaline species responsible for nearly all gem tourmaline, occurring in every color of the rainbow.
mineral
Jasper
An opaque, often colorfully patterned variety of chalcedony quartz, popular for tumbling, carving, and jewelry.
mineral
Calc-Silicate Rock
A metamorphic rock of calcium-rich silicate minerals formed from impure limestone or dolomite altered by heat and fluids.
metamorphic
Green Agate
A green-hued banded chalcedony, ranging from natural soft greens to brightly dyed commercial stones.
gemstone
Plume Agate
A translucent agate containing delicate three-dimensional feather- or plant-like plumes of mineral inclusions suspended in chalcedony.
gemstoneTripolite
A soft, lightweight siliceous sedimentary rock made of fossil diatom remains, prized as a fine natural abrasive and polishing powder.
sedimentary