Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Metabasalt
Basalt that has been metamorphosed, developing new minerals like chlorite, actinolite, and epidote that give it a greenish color.
metamorphic
Dalmatian Jasper
A cream-colored spotted stone resembling a Dalmatian dog, made of feldspar and quartz dotted with dark mineral grains.
igneous
Metagabbro
Coarse-grained gabbro that has been metamorphosed, partly recrystallizing into amphibole, plagioclase, and other metamorphic minerals.
metamorphic
Aquamarine Matrix
Aquamarine crystals still attached to their natural host rock, prized as mineral specimens showing beryl in its original pocket setting.
mineral
Gneiss
A high-grade metamorphic rock defined by alternating light and dark mineral bands, formed under intense heat and pressure.
metamorphicMarl
A soft, earthy sedimentary rock made of a mixture of calcium carbonate and clay, intermediate between limestone and mudstone.
sedimentary
Acanthite
A silver sulfide that is one of the most important silver ore minerals, forming dark metallic crystals and wires.
mineral
Aventurine Feldspar
A feldspar, better known as sunstone, that sparkles with metallic glints from tiny mineral platelets, an effect called aventurescence.
gemstone
Suevite
A rare breccia formed by meteorite impact, containing shocked rock fragments and glassy melt blobs welded together.
metamorphicGold Sheen Obsidian
A black obsidian displaying a golden metallic sheen caused by light reflecting off aligned microscopic gas bubbles or mineral inclusions.
igneous
Galena
A heavy, lead-grey metallic mineral with perfect cubic cleavage, galena is the world's main ore of lead and often carries silver.
mineralEltyubyuite
A rare chlorine-bearing iron garnet-supergroup mineral, the ferric analogue of wadalite, formed in high-temperature combustion-metamorphic rocks.
mineralBronze Sheen Obsidian
Black volcanic glass with a warm bronze or coppery sheen produced by light reflecting off aligned microscopic inclusions.
igneous
Feruvite
A calcium- and ferrous-iron-rich tourmaline, the iron analogue of uvite, forming dark brown to black crystals in skarns and metamorphic rocks.
mineral
Limonite
Limonite is an amorphous brown iron oxide ore, the rust-colored material behind ochre pigments and bog iron.
mineral
Bauxite
An earthy aluminum-rich residual rock and the world's principal ore of aluminum, often showing distinctive pea-like pisolites.
sedimentary
Hematite
The principal iron ore, a heavy iron oxide ranging from metallic silver-gray to earthy red, always leaving a tell-tale red-brown streak.
mineral
Albitite
A pale rock made almost entirely of the sodium feldspar albite, formed by sodic magmatism or sodium metasomatism.
igneous
Chromite
Chromite is the only commercial ore of chromium, a black iron-chromium oxide of the spinel group found in mafic igneous rocks.
mineral
Albite
The sodium end-member of the plagioclase feldspar series, a common white rock-forming mineral and parent of peristerite moonstone.
mineral
Calc-schist
A foliated metamorphic rock of calcite mixed with mica, quartz, and calc-silicate minerals, derived from marly sediments.
metamorphic
Siderite
Siderite is an iron carbonate ore, a brown rhombohedral mineral of the calcite group found in sediments and veins.
mineral
Jaspillite
A banded, metamorphosed iron formation in which bright red jasper alternates with silvery hematite or magnetite layers.
metamorphic
Kimberlite
A rare ultramafic volcanic rock that erupts from deep in the mantle and is the primary natural source of diamonds.
igneous