Rock & Mineral Encyclopedia

Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.

Tsilaisite

A manganese-dominant tourmaline, the source of bright yellow to greenish-yellow gem tourmaline, named for its Madagascar type locality.

A historic name for the red-violet to purplish lithium tourmaline first prized from Siberia, closely tied to the rubellite variety.

A calcium-magnesium tourmaline that forms in metamorphosed limestones, typically dark green to brown and often in well-formed crystals.

A rare iron-rich (ferric) species of the tourmaline group, dark brown to bronze-black, named after crystallographer Martin Buerger.

A calcium- and ferrous-iron-rich tourmaline, the iron analogue of uvite, forming dark brown to black crystals in skarns and metamorphic rocks.

A rare lithium-aluminum tourmaline with a vacant X site, typically pale pink to colorless and found in lithium pegmatites.

The lithium-rich tourmaline species responsible for nearly all gem tourmaline, occurring in every color of the rainbow.

A chromium-dominant tourmaline related to dravite, producing intensely deep green to blackish-green crystals from chromium-rich metamorphic rocks.

A rare ferric-iron-dominant tourmaline that forms in oxidized evaporite settings, appearing as black to red-brown prismatic crystals.

A rare calcium-rich lithium tourmaline famous for the spectacular concentric color zoning seen in polished cross-section slices.

The classic green gem variety of elbaite tourmaline, ranging from bright grass-green to deep forest tones colored by iron or chromium.

A distinctive tourmaline-rich granite from Cornwall, prized as an ornamental stone for its pink feldspar set with radiating black tourmaline.

A banded, metamorphosed iron formation in which bright red jasper alternates with silvery hematite or magnetite layers.

Ancient chemically deposited rock of alternating iron-oxide and silica bands recording Earth's early oxygenation and a major iron ore source.