Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Red Obsidian
Volcanic glass tinted red by fine iron-oxide inclusions, often blended with black to form mahogany-patterned obsidian.
crystal
Olenite
A rare aluminum-rich species of the tourmaline group, usually colorless to pale, named for the Olenii Range in Russia's Kola Peninsula.
mineral
Pele's Tears
Small, smooth, teardrop-shaped beads of basaltic volcanic glass formed from airborne lava droplets, often paired with Pele's hair.
igneous
Fenite
A metasomatic rock formed when alkali-rich fluids from carbonatite or alkaline intrusions transform surrounding country rock.
metamorphic
Baddeleyite
A natural zirconium dioxide mineral, hard and refractory, valued as a zirconium source and prized for high-precision U-Pb dating.
mineral
Plagioclase
The most abundant rock-forming feldspar group, a continuous solid-solution series from sodium albite to calcium anorthite that builds much of the crust.
mineral
Pyrite
The brassy iron sulfide mineral famous as 'fool's gold,' known for sharp metallic cubes and a much higher hardness than real gold.
mineral
Pele's Hair
Fine, golden, hair-like strands of basaltic volcanic glass spun from fluid lava droplets during eruptions, named for the Hawaiian volcano goddess.
igneous
Brown Jasper
An opaque earth-toned jasper colored brown by iron oxides, ranging from pale tan to deep chocolate.
mineral
Golden Healer Quartz
Quartz colored or coated by golden iron oxides such as limonite or goethite, giving a warm sunlit yellow glow.
crystal
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
Andradite Garnet
The calcium-iron garnet species, ranging from brilliant green demantoid to golden topazolite and jet-black melanite.
gemstone
Foitite
A rare alkali-deficient tourmaline whose X crystal site is largely vacant, giving slender dark blue to bluish-black crystals.
mineral
Schorl
The common iron-rich black variety of tourmaline, by far the most abundant tourmaline species and a popular grounding crystal.
mineralEulysite
A rare, dense iron-rich metamorphic rock composed of fayalite, iron pyroxene, and almandine garnet.
metamorphicRed Sandstone
Iron-stained sandstone whose red color comes from hematite coatings, formed in oxidizing desert, river, and coastal environments.
sedimentary
Uraninite
Uraninite is the chief radioactive uranium ore, a dense black oxide and the historic source of radium and uranium.
mineral
Hausmannite
A brownish-black manganese oxide and important manganese ore, forming pseudo-octahedral crystals with a chestnut-brown streak.
mineral
Cassiterite
Tin oxide and the principal ore of tin, a dense, hard mineral mined since the Bronze Age for tin metal.
mineral
Rutile
Rutile is a major titanium ore and the famous golden needle inclusion that gives rutilated quartz its shimmering threads.
mineral
Anatase
A tetragonal titanium dioxide polymorph forming steep bipyramidal crystals, often deep blue to black with brilliant adamantine luster.
mineral
Zincite
A rare zinc oxide best known for its deep red to orange color, classically from Franklin, New Jersey, and as colorful man-made crystals.
mineral
Black Tourmaline
The opaque black iron-rich variety of tourmaline (schorl), forming striated prismatic crystals popular as a protective grounding stone.
mineral
Columbite
A black iron-manganese niobate that is a primary ore of niobium, forming a continuous series with tantalite (together called coltan).
mineral