Black Tourmaline

Hardness: 7-7.5 on Mohs scale; Color: typically opaque black, can be dark blue or dark green; Luster: vitreous (glassy) to resinous; Crystal structure: trigonal, often forming prismatic crystals with vertical striations, frequently acicular (needle-like) or columnar; Cleavage: indistinct; Specific Gravity: 3.06-3.26

Formed in igneous and metamorphic rocks, especially in granites, granite pegmatites, and high-temperature hydrothermal veins. Also found in some sedimentary rocks as detrital grains. Its formation often occurs during late-stage crystallization of magmas or during regional metamorphism under conditions of boron enrichment. Geological age varies widely depending on the specific deposit, ranging from Precambrian to relatively recent.

Black Tourmaline is popular as a collector's mineral and is occasionally cut into cabochons for jewelry, though its opacity limits its use. Industrially, tourmaline is used in pressure gauges and other electrical applications due to its piezoelectric properties. It's also often used in metaphysical practices for protection and grounding.

Black Tourmaline (Schorl) is the most common variety of tourmaline, accounting for about 95% of all natural tourmaline. The name 'tourmaline' comes from the Sinhalese word 'turmali,' meaning 'mixed colored stones,' though schorl itself is typically black. It exhibits pyroelectricity, meaning it can generate an electrical charge when heated or cooled. It's also piezoelectric, generating an electrical charge when subjected to pressure.

In the field, Black Tourmaline is identifiable by its characteristic black color, vitreous luster, and often distinctly prismatic, elongated crystals with vertical striations. It's generally opaque and can be found in various sizes, from small needles to large columns. It often occurs embedded in quartz, feldspar, and mica-rich rocks. Common locations include Brazil, Pakistan, Afghanistan, the United States (Maine, California), and Africa. When identifying, look for its sturdy, often elongated crystal habit. Its hardness helps distinguish it from softer black minerals like hornblende or biotite.