Mineralpedia Details for Schorl

A Tourmaline group mineral named for the Old German word schürl, a word of unknown derivation which may mean “impurities,” or may be in reference to an old German village called Schorl, now called Zorschlau, which had a nearby tin mine that contained Schorl. Schorl is the most common of the tourmalines and can be found in many localities, but a few know for exceptional specimens include Germany, England, Italy, Russia, the USA, Mexico, Brazil, Namibia, and Afghanistan. Schorl is a common constituent of granite and granite pegmatites, can be found in hydrothermal veins and metamorphic rocks, and is occasionally found as a detrital mineral. Schorl is pyroelectric, has a charge when heated, and piezoelectric, forms a charge in response to pressure.

Ref. Handbook of Mineralogy, Anthony et al (1995) and MSA at http://www.handbookofmineralogy.org/pdfs/schorl.pdf

Formula

NaFe²⁺₃Al₆(BO₃)₃Si₆O₁₈(OH)₄ 

Crystal System

Trigonal 

Crystal Habit

Acicular, Prismatic, Striated 

Cleavage

Indistinct, None, None 

Luster

Vitreous (Glassy) 

Color

black, brownish black, greenish black, bluish black 

Streak

brown 

Class

Trigonal - Ditrigonal Pyramidal 

Fracture

Brittle - Conchoidal 

Hardness

7.5 

WebMineral

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Mindat

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Schorl Tourmaline to 2.5cm.

A terminated 5.5cm striated, black Schorl tourmaline crystals with snow white Albite crystals.

This is a cap from a larger prismatic crystal with an extreme pyramidal termination not generally seen in large crystals of tourmaline like this.

An excellent grouping of black lustrous crystals of trigonally terminated Schorl crystals to 5-8mm.

Lustrous deep black nicely terminated Schorl tourmaline. E

Special Info

Chris van Laer Collection

Stubby, striated Schorl crystal with TEN faces on the termination. From this area, it is an excellent specimen from the miarolitic cavities.

A former Schorl crystal completely replaced by very fine, dark green Lepidolite. 

Special Info

Illustrated in London's book "Pegmatites"

This specimen is illustrated on page 185, Fig. 12-6a of London's book called "Pegmatites".

This specimen of Schorl tourmaline exhibits the intergrowth with Quartz much like Quartz -Microcline graphite granite. One of the interesting features of Schorl in pegmatites is the nucleation of tourmaline along the contact zone of pegmatite with the wall-rock. At this contact tourmaline begins to grow rapidly toward the center of the pegmatite and perpendicular to the wall. Tourmaline is a cyclosilicate and crystallizes like a spiral outward from that original point of nucleation with the wall. All crystals of Schorl will compete for the boron in solution and rapid crystallization produces divergent crystals.