Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Diamond
The hardest known natural material, a crystalline form of pure carbon prized as the ultimate gemstone for its brilliance and fire.
gemstone
Chrome-Dravite
A chromium-dominant tourmaline related to dravite, producing intensely deep green to blackish-green crystals from chromium-rich metamorphic rocks.
mineral
Blue Kyanite
A striking blue aluminum silicate famous for bladed crystals and anisotropic hardness that differs dramatically along and across the blade.
mineral
Particolored Tourmaline
A tourmaline displaying two or more distinct colors in a single crystal, prized for natural color zoning like watermelon and bicolor stones.
gemstone
Danburite
A glassy calcium borosilicate forming wedge-tipped prismatic crystals, usually colorless to pale yellow or pink, sometimes faceted as a gem.
crystal
Agate
A banded variety of chalcedony quartz, famed for its colorful concentric layers and enormous range of patterns and colors.
mineral
Mocha Agate
A pale translucent chalcedony threaded with brown-black manganese and iron dendrites that mimic tiny ferns, mosses or landscapes.
gemstone
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
Gahnite
A hard zinc-rich member of the spinel group, usually dark blue-green to black, forming octahedral crystals in metamorphic and pegmatitic rocks.
mineral
Black Tourmaline
The opaque black iron-rich variety of tourmaline (schorl), forming striated prismatic crystals popular as a protective grounding stone.
mineral
Pulaskite
A coarse-grained alkali syenite of perthitic feldspar with sodic pyroxene or amphibole and minor nepheline, from Pulaski County, Arkansas.
igneous
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 Obsidian
A pale, partly crystallized volcanic glass; genuinely white obsidian is uncommon and usually reflects devitrification or spherulitic growth in the glass.
igneous
Appinite
A group of coarse, water-rich plutonic rocks dominated by large hornblende crystals set in feldspar, intermediate between lamprophyre and diorite.
igneous
Kersantite
A dark mica lamprophyre with biotite and augite phenocrysts in a plagioclase-dominated groundmass, the feldspar counterpart of minette.
igneous
Adularia
A low-temperature potassium feldspar famous for forming transparent Alpine crystals and the gem moonstone, which shows a floating blue sheen called adularescence.
mineral
Shonkinite
A dark, mafic potassic alkaline rock rich in augite with alkali feldspar and often nepheline, classically forming the base of layered sills.
igneous
Champagne Tourmaline
A soft brown to golden-brown tourmaline with warm, neutral tones reminiscent of sparkling champagne.
gemstone
Pyrargyrite
A silver antimony sulfosalt known as dark ruby silver, an important silver ore with deep red internal reflections.
mineral
Anthracite
The highest-rank coal, a hard, lustrous black rock that burns cleanly with little smoke and high heat output.
metamorphic
White Opal
The most common precious opal, with a pale milky body that shows softer pastel flashes of play-of-color throughout.
gemstone
Spessartite Garnet
A manganese aluminum garnet glowing in vivid orange to reddish-orange tones, with the finest called mandarin garnet.
gemstone
Rock Salt
An evaporite rock of the mineral halite (sodium chloride), the source of common salt, with a distinctive salty taste.
sedimentary
Pezzottaite
A rare cesium-rich, beryl-related gem mineral with a raspberry-pink color, first found in Madagascar in 2002.
gemstone