Black Tourmaline

Black tourmaline is a natural mineral, usually schorl, the iron-rich sodium tourmaline and the most common member of the tourmaline group. In the trade black tourmaline is sold as schorl, and the Japanese laboratory association AGL lists "schorl" as an alias of black tourmaline. It is common in granites, pegmatites and metamorphic rocks and is rarely used as a gem.

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Tourmaline (black)
Tourmaline (black)

4mm / 6mm / 8mm / 10mm

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Full material guide
Material facts

What the material is, where it comes from or how it is made, identification and care, from the cited sources.

Properties

Nature Natural mineral
Mineral group Tourmaline group
Mineral species Schorl
Chemical formula NaFe²⁺₃Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH)
Color Bluish black to black, sometimes brownish black, rarely greenish black
Crystal system Trigonal
Mohs hardness 7
Specific gravity 3.18 to 3.22
Refractive index nω 1.660–1.672, nε 1.635–1.650
Birefringence 0.022 to 0.025
Cleavage Poor / indistinct
Luster Vitreous to resinous
Streak Grayish white to bluish white
Transparency Translucent to opaque

Origins & sources

Schorl forms in a wide variety of rock types: granites and granitic pegmatites, high-temperature hydrothermal veins and metamorphic rocks. Its most common occurrence is as millimeter-size crystals scattered through granite, pegmatite or gneiss as an accessory mineral, rarely more than a few percent of the rock. The name comes from the village now called Zschorlau in Saxony, Germany, whose nearby tin mine yielded much black tourmaline.

Identification

Black tourmaline is recognized by prismatic crystals with rounded triangular cross-sections that are often striated along their length, a lack of visible cleavage, a vitreous luster and a hardness of about 7; any specimen with obvious cleavage is probably not tourmaline. Its refractive indices (about 1.635–1.672) and birefringence (0.022–0.025) are higher than those of elbaite. Not every nearly black tourmaline is schorl: GIA notes that some dravite-uvite tourmalines are brown to nearly black. Tourmaline is pyroelectric: when warmed, for example under display lights, it gains a slight electrical charge and attracts dust.

Care

GIA rates tourmaline 7 to 7.5 on the Mohs scale and generally suitable for everyday wear. It is usually stable to light and most chemicals, but heat can be damaging. Clean with warm, soapy water and a soft brush; ultrasonic and steam cleaners are not recommended.

History & culture

History

The name schorl was in use before 1400, when the village now called Zschorlau in Saxony was named "Schorl"; it was first mentioned by Ulrich Rülein von Calw in 1505, and Johannes Mathesius described "schürl" from tin mines of the Saxony Ore Mountains in 1562. In English, "shorl" and "shirl" were used in the 18th century, and "schorl" and "iron tourmaline" in the 19th. GIA notes that schorl is rarely used as a gem, although it has been featured in mourning jewelry.

Cultural meanings

GIA reports that different tourmaline colors are thought to have their own properties; black tourmaline is believed to protect the wearer and give a sense of self-confidence. These are beliefs, not verified effects.

Traditional beliefs

According to GIA, tourmaline is an October birthstone and the gem given for the eighth wedding anniversary; GIA also records that ancient mystics believed tourmaline could inspire artistic expression.

Sources

Collected Oct 23, 2026