The Crystal
Encyclopedia

Achroite

Achroite is the rare, colorless variety of tourmaline (often elbaite or fluor-elbaite). It forms trigonal, prismatic ...

Afghanite

Afghanite is a rare cancrinite-group feldspathoid (tectosilicate) known for blue to colorless material, often associa...

Agate

Agate is a banded variety of chalcedony quartz.

Ajoite

Ajoite is a rare copper silicate mineral most commonly found as inclusions within quartz.

Alexandrite

Alexandrite is a rare color-changing variety of chrysoberyl that shifts from green in daylight to red under incandesc...

Almandine

Almandine is an iron-aluminum garnet commonly deep red in color.

Amazonite

Amazonite is a green variety of microcline feldspar.

Amber

Amber is fossilized tree resin valued for warmth, color, and historical use.

Amethyst

Amethyst is a purple variety of quartz colored by iron impurities and natural irradiation, forming in volcanic and hy...

Ametrine

Ametrine is a naturally occurring combination of amethyst and citrine within a single quartz crystal, caused by uneve...

Ammolite

Ammolite is an opal-like organic gemstone formed from fossilized ammonite shells.

Andalusite

Andalusite is an aluminum silicate mineral often showing pleochroism.

Chiastolite

Chiastolite is a variety of andalusite distinguished by a natural cross-shaped carbon inclusion formed during crystal...

Angelite

Angelite is a blue form of anhydrite created when gypsum loses its water content under geological pressure.

Anglesite

Anglesite is a lead sulfate mineral formed through oxidation of galena.

Ankerite

Ankerite is a calcium iron magnesium carbonate mineral closely related to dolomite, commonly forming rhombohedral cry...

Antigorite

Antigorite is a serpentine-group mineral formed through metamorphism of ultramafic rocks.

Apatite

Apatite is a group of phosphate minerals commonly used as a source of phosphorus.

Apophyllite

Apophyllite is a hydrated potassium calcium silicate that forms well-defined prismatic crystals in volcanic environme...

Aquamarine

Aquamarine is a blue variety of beryl colored by iron impurities, forming in granitic pegmatites.

Aquatine Calcite

Aquatine Calcite is a blue calcite variety colored by copper and other trace minerals, forming in sedimentary environ...

Aragonite

Aragonite is a polymorph of calcium carbonate that forms in marine and sedimentary environments under high pressure.

Arfvedsonite

Arfvedsonite is a sodium-rich amphibole mineral forming prismatic crystals in alkaline igneous rocks.

Aura Quartz

Aura Quartz is natural quartz bonded with vapor-deposited metals such as titanium or gold to create an iridescent sur...

Azurite

Azurite is a copper carbonate mineral often associated with malachite.

Barite

Barite is a barium sulfate mineral forming tabular crystals.

Benitoite

Benitoite is a rare barium titanium silicate mineral best known from California, where it forms in serpentine-hosted ...

Red Beryl

Red Beryl is a rare manganese-colored variety of beryl, forming hexagonal crystals in rhyolite deposits.

Bismuth Crystal

Bismuth crystals are typically lab-grown from elemental bismuth, forming stepped hopper crystals as the metal cools a...

Black Kyanite

Black kyanite forms as bladed crystal aggregates in metamorphic rocks, often exhibiting strong directional hardness.

Black Tourmaline

Black tourmaline (schorl) is an iron-rich tourmaline commonly forming prismatic crystals in igneous and metamorphic r...

Bloodstone

Bloodstone is a green chalcedony variety colored by iron oxide inclusions that create red spotting.

Blue Apatite

Blue apatite is a phosphate mineral commonly forming prismatic crystals in igneous and metamorphic rocks.

Blue Aragonite

Blue aragonite is a calcium carbonate polymorph formed in sedimentary environments, often colored by copper.

Blue Calcite

Blue calcite is a calcium carbonate mineral with calming coloration.

Blue Halite

Blue halite is a rare sodium chloride crystal colored by lattice defects and radiation exposure.

Blue John Fluorite

Blue John is a banded fluorite variety unique to Derbyshire, England.

Blue Kyanite

Blue kyanite forms bladed crystals with directional hardness in metamorphic rocks.

Blue Lace Agate

Blue lace agate is a banded chalcedony known for its delicate blue coloration.

Blue Onyx

Blue onyx is a banded chalcedony variety often enhanced by dyeing.

Blue Tiger’s Eye

Blue Tiger’s Eye is a fibrous quartz variety formed through the alteration of crocidolite fibers, creating a silky bl...

Bornite

Bornite is a copper iron sulfide mineral known for its iridescent tarnish caused by surface oxidation.

Botswana Agate

Botswana Agate is a banded chalcedony formed in volcanic rock cavities.

Bronzite

Bronzite is an iron-rich variety of enstatite displaying metallic schiller.

Brookite

Brookite is a rare titanium dioxide polymorph forming tabular crystals.

Brookite Quartz

Quartz containing inclusions of brookite titanium oxide.

Bustamite

Bustamite is a manganese calcium silicate related to rhodonite.

Calcite

Calcite is a calcium carbonate mineral forming in sedimentary, metamorphic, and hydrothermal environments.

Cancrinite

Cancrinite is a sodium calcium aluminosilicate found in alkaline igneous rocks.

Caribbean Calcite

A trade name for blue calcite with aragonite matrix.

Carnelian

A red to orange variety of chalcedony colored by iron oxides.

Cassiterite

Cassiterite is the primary ore of tin, forming in hydrothermal veins.

Cavansite

Rare vanadium-bearing silicate forming in basalt cavities

Celestite

Strontium sulfate mineral forming tabular crystals

Cerussite

Lead carbonate mineral with high adamantine luster

Chalcanthite

Highly soluble copper sulfate mineral

Chalcedony

Microcrystalline quartz composed of silica fibers

Chalcocite

Copper sulfide mineral and major copper ore

Charoite

Rare fibrous silicate mineral found only in Russia

Cherry Quartz

Man-made quartz glass infused with cinnabar coloring

Chlorite Phantom Quartz

Quartz crystal containing chlorite phantom inclusions

Chromite

Primary ore of chromium

Chrysanthemum Stone

Sedimentary stone with radiating mineral formations

Chrysocolla

Hydrated copper silicate mineral

Chrysoprase

Nickel-bearing variety of chalcedony

Cinnabar

Mercury sulfide mineral and primary mercury ore

Citrine

Yellow variety of quartz colored by iron

Clear Quartz

Pure crystalline silica

Clinozoisite

Calcium aluminum silicate mineral

Cobaltoan Calcite

Cobalt-bearing variety of calcite

Color Change Fluorite

Fluorite exhibiting photochromic color shifts

Copper

Naturally occurring metallic copper

Coral Fossil

Crazy Lace Agate

Banded chalcedony variety

Cuprite

Copper(I) oxide mineral

Danburite

Calcium boron silicate mineral

Datolite

Calcium boron silicate hydroxide mineral

Desert Glass

Natural silica glass formed by impact heat

Desert Rose

Gypsum crystals formed in arid sand

Diopside

Calcium magnesium silicate mineral

Dioptase

Copper silicate hydroxide mineral

Dolomite

Calcium magnesium carbonate mineral

Druzy Quartz

Fine crystal aggregates on host rock

Dumortierite

Aluminum borosilicate mineral

Ekanite

Rare thorium-bearing silicate mineral

Elestial Quartz

Complex layered quartz growth formation

Emerald

Green chromium-bearing beryl variety

Enstatite

Magnesium silicate pyroxene mineral

Epidote

Calcium aluminum iron silicate mineral

Faden Quartz

Quartz crystal with healed internal fracture line

Feldspar

Group of rock-forming aluminosilicates

Fire Agate

Iridescent chalcedony variety

Fire Opal

Transparent to translucent opal variety

Fire Quartz

Quartz with hematite inclusions

Flint

Microcrystalline quartz variety

Fluellite

Rare hydrated aluminum phosphate mineral containing fluorine

Fluorite

Calcium fluoride mineral

Fossil Coral

Fossilized coral replaced by calcite

Fuchsite

Chromium-rich muscovite mica

Galena

Primary lead ore mineral

Garnet

Group of silicate minerals

Garnet (Grossular)

Calcium-aluminum silicate garnet variety

Garnet (Spessartine)

Manganese aluminum silicate garnet

Garnet (Uvarovite)

Chromium-rich calcium garnet

Gaspeite

Nickel magnesium carbonate mineral

Goethite

Iron oxyhydroxide mineral common in soils

Golden Healer

Quartz variety colored by iron oxide inclusions

Goldstone

Artificial glass containing suspended copper crystals

Goshenite

Colorless variety of beryl

Grape Agate

Botryoidal chalcedony formation

Green Aventurine

Quartz variety containing fuchsite inclusions

Green Calcite

Carbonate mineral colored by trace elements

Green Fluorite

Calcium fluoride mineral

Green Kyanite

Aluminum silicate polymorph

Green Opal

Hydrated silica mineraloid

Green Tourmaline

Borosilicate mineral group

Hackmanite

Sulfur-bearing sodalite variety with tenebrescence

Pink Halite

Naturally occurring sodium chloride colored by trace minerals

Hematite

Iron oxide mineral and major iron ore

Rainbow Hematite

Hematite with thin-film interference coating

Hemimorphite

Hydrated zinc silicate mineral

Herkimer Diamond

Double-terminated quartz crystals

Heulandite

A hydrated zeolite mineral forming monoclinic crystals

Hiddenite

A chromium-bearing green variety of spodumene

Honey Calcite

A yellow variety of calcite colored by iron inclusions

Howlite

A borate mineral often used as a decorative stone

Blue Howlite

Dyed howlite commonly sold as turquoise substitute

Indigo Gabbro

A coarse-grained mafic igneous rock rich in plagioclase and pyroxene

Iolite

A pleochroic magnesium aluminum silicate mineral

Iolite (Water Sapphire)

A pleochroic variety of cordierite historically used for navigation

Jade

A term for two distinct minerals jadeite and nephrite

Jade (Actinolite)

An amphibole mineral forming nephrite jade

Jade (Nephrite)

A tough fibrous amphibole mineral historically carved and polished

Jasper

An opaque microcrystalline variety of quartz

Jasper (Fancy)

A multicolored ornamental jasper variety

Jet

Fossilized wood compressed under pressure over millions of years

Kambaba Jasper

A stromatolite jasper containing fossilized algae structures

Kammererite

A chromium-rich variety of clinochlore

Kornerupine

A rare borosilicate mineral sometimes used as a gemstone

Kunzite

A pink variety of spodumene colored by manganese

Kyanite

A bladed crystal known for variable hardness

Labradorite

A feldspar mineral known for labradorescence

Labradorite (Spectrolite)

A high-flash variety of labradorite from Finland

Lapis Lazuli

A metamorphic rock primarily composed of lazurite

Larimar

A rare blue variety of pectolite formed in volcanic cavities

Lazulite

A rare phosphate mineral often confused with lapis lazuli

Lemon Quartz

A heat-treated or irradiated variety of quartz with yellow coloration

Lemurian Quartz

A quartz variety identified by horizontal growth striations on crystal faces

Lepidocrocite

An iron oxide mineral commonly found as inclusions in quartz

Lepidolite

A lithium-rich mica mineral often used as a lithium ore

Libyan Desert Glass

A natural silica glass formed by meteorite impact or extreme heat

Limonite

A secondary mineral formed from the weathering of iron-rich minerals

Llanite

A rhyolitic rock composed primarily of quartz and feldspar

Lodestone

A naturally magnetic form of magnetite

Mahogany Obsidian

A variety of obsidian with iron inclusions causing brown mottling

Malachite

A copper carbonate hydroxide mineral forming in oxidation zones of copper deposits

Malachite (Fibrous)

Fibrous malachite is a copper carbonate hydroxide mineral forming in radiating structures.

Marcasite

A polymorph of pyrite with orthorhombic crystal structure

Maw-Sit-Sit

A chromium-rich jadeite-related rock

Merlinite

A patterned quartz often misclassified as dendritic opal

Mica

A group of sheet silicate minerals with perfect cleavage

Microcline

A potassium feldspar mineral including amazonite varieties

Moldavite

A natural glass formed from meteorite impact

Moonstone

A feldspar mineral exhibiting adularescence

Black Moonstone

A darker variety of moonstone feldspar

Morganite

A pink variety of beryl colored by trace manganese

Moss Agate

A chalcedony variety with mineral inclusions resembling moss

Neptunite

A rare titanium silicate often found with benitoite

Nuummite

One of the oldest known minerals on Earth, composed mainly of gedrite and anthophyllite

Obsidian

A naturally occurring volcanic glass formed from rapidly cooled lava

Gold Sheen Obsidian

Obsidian containing gas bubbles that reflect light, creating a golden sheen

Rainbow Obsidian

Ocean Jasper

A rare orbicular jasper found exclusively along Madagascar’s coast

Oligoclase

A plagioclase feldspar intermediate between albite and anorthite

Onyx

A banded variety of chalcedony typically black and white

Green Onyx

Green onyx is a banded chalcedony variety colored by trace minerals.

Opal

An amorphous hydrated silica known for play-of-color

Boulder Opal

Opal formed naturally within ironstone matrix

Peruvian Pink Opal

A common opal variety colored by trace organic compounds

White Opal

A light-colored opal often displaying subtle play-of-color

Orange Calcite

A colored calcite variety caused by iron impurities

Orca Agate

A banded agate known for black-and-white layered patterns

Orpiment

A soft arsenic sulfide mineral historically used as pigment

Pargasite

A magnesium-rich amphibole mineral

Pearl

An organic gemstone formed within mollusks

Pectolite

A sodium calcium inosilicate mineral, Larimar is its blue variety

Peridot

A gem-quality variety of olivine formed in mantle rocks

Petalite

A lithium-bearing mineral associated with pegmatites

Petrified Wood

Fossilized wood replaced by silica over millions of years

Phenacite

A rare beryllium silicate with high hardness and brilliance

Phlogopite

A magnesium-rich mica mineral with flexible sheets

Phosphosiderite

A hydrated iron phosphate mineral commonly forming nodules and masses

Pietersite

A brecciated quartz with fibrous inclusions creating chatoyancy

Pink Amethyst

A pink-colored variety of quartz related to amethyst and hematite inclusions

Pink Opal

A common opal variety colored by organic compounds or trace minerals

Prehnite

A calcium aluminum silicate mineral forming botryoidal and crystalline masses

Prehnite with Epidote

Prehnite crystals associated with epidote inclusions in metamorphic rock

Proustite

A silver arsenic sulfide mineral known for deep red transparency

Psilomelane

A hard manganese oxide mineral occurring in botryoidal masses

Purpurite

A manganese phosphate mineral known for its vivid purple color

Pyrite

An iron sulfide mineral forming cubic and pyritohedral crystals

Pyromorphite

A lead phosphate chloride mineral forming prismatic hexagonal crystals

Harlequin Quartz

Clear quartz containing red hematite inclusions creating a harlequin pattern

Rainbow Obsidian

Volcanic glass with microscopic inclusions causing iridescent color bands

Rhodochrosite

A manganese carbonate mineral known for its vivid pink coloration

Rhodolite Garnet

A pyrope-almandine garnet variety valued for purplish-red hues

Rhodonite

A manganese silicate mineral often showing black manganese oxide veining

Rhyolite

A fine-grained volcanic rock chemically similar to granite

Rose Quartz

A pink variety of quartz colored by trace titanium or dumortierite

Roselite

A rare cobalt calcium arsenate mineral known for vivid pink coloration

Ruby

A red variety of corundum colored by trace chromium

Ruby Fuchsite

Ruby crystals naturally embedded within chromium-rich fuchsite mica

Ruby in Zoisite

Ruby crystals naturally embedded within green zoisite matrix

Rutilated Quartz

Quartz containing needle-like rutile inclusions

Rutile

A titanium oxide mineral often found as inclusions

Saffordite

A rare tektite formed from meteorite impact

Sapphire

A gemstone variety of corundum excluding red

Sardonyx

A banded variety of chalcedony combining sard and onyx

Scapolite

A group of sodium-calcium aluminosilicate minerals

Scheelite

A calcium tungstate mineral with fluorescent properties

Scolecite

A zeolite mineral forming needle-like crystals

Selenite

A crystalline variety of gypsum formed through evaporation

Peach Selenite

A peach-colored gypsum variety colored by iron inclusions

Septarian

A concretion formed from sedimentary calcite and aragonite

Seraphinite

A chatoyant chlorite mineral with fibrous inclusions

Serpentine

A group of hydrated magnesium silicate minerals

Bowenite

A harder, gem-quality variety of serpentine

Shattuckite

A rare copper silicate mineral formed in oxidized zones

Shiva Lingam

A cryptocrystalline quartz river stone shaped naturally

Shungite

A carbon-rich mineraloid containing fullerenes

Elite Shungite

A rare high-carbon form of shungite with metallic luster

Smithsonite

A zinc carbonate mineral often found in botryoidal form

Smoky Quartz

A quartz variety colored by natural radiation exposure

Sodalite

Sodium aluminum silicate mineral often associated with calcite

Specular Hematite

Crystalline variety of hematite with reflective plate-like crystals

Sphalerite

Primary ore of zinc with high dispersion and resinous luster

Spinel

Magnesium aluminum oxide often mistaken historically for ruby

Red Spinel

Red variety of spinel prized as a gemstone

Spirit Quartz

Quartz crystal with secondary crystal overgrowth

Staurolite

Aluminum iron silicate commonly forming cross twins

Stibnite

Stibnite is an antimony sulfide mineral forming elongated prismatic crystals.

Stilbite

Hydrated sodium calcium aluminum silicate

Stromatolite

Fossilized cyanobacteria mats forming layered rock

Sugilite

Potassium sodium lithium silicate mineral

Sunstone

Plagioclase feldspar with aventurescence

Super Seven Melody Stone

Super Seven variety popularized by Melody

Tanzanite

Blue-violet variety of zoisite colored by vanadium

Tektite

Glass formed from meteorite impacts on Earth

Thulite

Manganese-rich pink variety of zoisite

Tibetan Quartz

Naturally etched quartz from Himalayan deposits

Tiger Iron

Natural combination of tiger’s eye; hematite; jasper

Tiger’s Eye

Quartz pseudomorph after crocidolite

Red Tiger’s Eye

Heat-treated variety of tiger’s eye with enhanced red tones

Titanite

Calcium titanium silicate mineral with high dispersion

Topaz

Aluminum fluorosilicate mineral with high hardness

Imperial Topaz

Rare orange-pink variety of topaz colored by chromium

Tourmalinated Quartz

Clear quartz containing black tourmaline inclusions

Tourmaline

Tourmaline is a complex borosilicate mineral group with wide color variation.

Blue Tourmaline

Blue variety of tourmaline also known as indicolite

Pink Tourmaline

Pink elbaite tourmaline variety

Trolleite

Rare aluminum phosphate mineral often mixed with quartz

Turquoise

Hydrated copper aluminum phosphate mineral

Ulexite

Hydrated sodium calcium borate known as TV stone

Unakite

Unakite is a composite igneous rock composed of epidote, feldspar, and quartz.

Uraninite

Uraninite is a uranium oxide mineral and primary uranium ore.

Vanadinite

Lead vanadate chloride mineral

Variscite

Hydrated aluminum phosphate mineral

Vesuvianite

Complex calcium aluminum silicate mineral

Vivianite

Hydrated iron phosphate mineral that darkens with light

Wavellite

Hydrated aluminum phosphate forming radiating clusters

Weloganite

Rare hydrated sodium strontium carbonate mineral

Wulfenite

Wulfenite is a lead molybdate mineral known for thin tabular crystals.

Yellow Fluorite

Calcium fluoride mineral with cubic crystallization

Zebra Jasper

Banded chalcedony variety of quartz

Zeolite (Mix)

Group of hydrated aluminosilicate minerals

Zincite

Zinc oxide mineral often found as furnace byproduct

Zircon

Zircon is a zirconium silicate mineral known for brilliance and durability.

Zoisite

Zoisite is a calcium aluminum silicate mineral occurring in several varieties.