Schorl

Schorl is the black variety of tourmaline.  The name is associated with the village of Zschorlau in Saxony Germany which was named "Schorl" prior to the year 1400. A tin mine with a lot of black tourmaline was located near the village.  According to gemdat.com, Schorl was named after an old mining expression for "false ore".  .

ï  Mineral: Schorl aka black tourmaline

ï  Chemistry: Na(Fe²⁺₃)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH)

ï  Class: Cyclosilicate

ï  Crystal system: Hexagonal

ï  Color: Bluish-black to black, sometimes brownish-black, rarely greenish-black.

ï  Refractive index:  1.635 – 1.672

ï  Luster: Vitreous, resinous

ï  Specific gravity: 3.18-3.22

ï  Mohs Hardness: 7

ï  Cleavage: Poor/indistinct

ï  Fracture: Irregular/uneven, sub-conchoidal

Schorl is pyroelectric - taking a charge when heated, and piezoelectric - forming a charge in response to pressure.  It is strongly dichroic - changing color based on crystal orientation - yellow brown to pale yellow in one direction, pale brown.   Schorl is the most common member of the Tourmaline group.  It is one of the most aesthetic black minerals known.  It can form in tiny needles within a Quartz crystal where it is known as Tourmalinated Quartz.

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. 

The primary use of tourmaline in general is as a semi-precious gemstone.  Tourmaline is a birthstone for the month of October and the gemstone of the 38^th Anniversary.

Some of the locales from which specimens of Schorl are available at Taos Rockers are:

Namibia

Brazil

China

Pakistan

Idaho

Melody, in her book Love Is In The Earth, says “Black Tourmaline can be used to both repel and to protect against negativity...It provides for an increase in ones physical vitality, emotional stability, and intellectual acuity…As a protective stone...”