Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Black Onyx
A solid jet-black chalcedony, usually a dyed and treated agate, prized for sleek polished beads, cabochons, and intaglios.
gemstone
Onyx
A banded variety of chalcedony quartz, classically black or black-and-white, long favored for cameos and beads.
gemstone
Black Agate
A deep black variety of banded chalcedony, often closely related to or treated like onyx, used for jewelry and carvings.
gemstone
Black Obsidian
Jet-black natural volcanic glass formed by rapidly cooled lava, prized for its glassy luster and razor-sharp conchoidal fracture.
igneous
Black Jasper
A dense, opaque black variety of microcrystalline quartz historically used as a touchstone for testing precious metals.
mineral
Black Moonstone
A dark gray-to-black feldspar variety of moonstone that shows blue and white adularescent flash against a smoky body.
gemstone
Black Garnet
An opaque black garnet — typically titanium-bearing melanite andradite — historically cut for mourning and Victorian jewelry.
gemstone
Black Shale
Dark, organic-rich fine-grained sedimentary rock formed in oxygen-poor waters, often a source rock for oil and gas.
sedimentary
Black Tourmaline
The opaque black iron-rich variety of tourmaline (schorl), forming striated prismatic crystals popular as a protective grounding stone.
mineral
Black Opal
The rarest and most valuable opal, with a dark body tone that makes its flashing rainbow play-of-color blaze brilliantly.
gemstoneOnyx Marble
Translucent banded calcium-carbonate stone deposited in caves and springs, prized for ornamental carvings despite its softness.
sedimentary
Franklinite
A black spinel-group zinc iron oxide, essentially unique to Franklin, New Jersey, where it was a key zinc and manganese ore.
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.
mineralSardonyx
A banded chalcedony combining reddish-brown sard with white or black onyx layers, prized since antiquity for carved cameos.
gemstoneJet
A lightweight black organic gemstone formed from fossilized wood under pressure, a type of lignite long used in mourning jewelry.
sedimentaryMidnight Obsidian
A trade name for deep, solid black obsidian, natural volcanic glass prized for its uniform jet-black color and glassy luster.
igneous
Flint
A hard, dark variety of chert that knaps into razor-sharp edges and sparks against steel, central to Stone Age technology.
sedimentary
Schorl
The common iron-rich black variety of tourmaline, by far the most abundant tourmaline species and a popular grounding crystal.
mineral
Rhodonite
A rose-pink manganese silicate marbled with black veins, prized as a tough ornamental and occasionally faceted gemstone.
mineral
Lightning Ridge Opal
Opal from Lightning Ridge, Australia, the world's premier source of black opal with brilliant color on a dark body.
gemstone
Kyanite
A bladed aluminosilicate famous for having two very different hardnesses depending on the direction you scratch it.
mineralSemiblack Opal
Opal with a dark grey body tone sitting between black and light opal, giving play-of-color rich contrast at an accessible price.
gemstone
Chromite
Chromite is the only commercial ore of chromium, a black iron-chromium oxide of the spinel group found in mafic igneous rocks.
mineral
Melanite Garnet
The titanium-rich black variety of andradite garnet, with a brilliant resinous luster prized for mourning and statement jewelry.
gemstone