Black Tourmaline

Hardness: 7-7.5 (Mohs scale); Color: Typically black, but can be dark brown, dark green, or dark blue; Luster: Vitreous to sub-vitreous, sometimes resinous; Crystal Structure: Hexagonal system, often occurring as prismatic crystals with striations parallel to the C-axis; Cleavage: None; Specific Gravity: 3.06-3.26.

Formation Process: Black tourmaline forms through hydrothermal processes in pegmatites and granitic rocks, as well as in some metamorphic rocks like schists and gneisses. It crystallizes from hot, mineral-rich fluids that seep into cracks and cavities in existing rocks. Geological Age: Varies depending on the specific geological event, but can be found in rocks ranging from Precambrian to Cenozoic.

Industry: Used in pressure gauges, as a source of boron in certain industrial processes. Jewelry: Popular as a gemstone, often cut into cabochons or faceted stones, and used in various forms of jewelry for its dark color and metaphysical properties. Other Uses: Often used in meditation practices and for grounding purposes in alternative healing.

Black tourmaline, also known as Schorl, is the most common variety of tourmaline, accounting for approximately 95% of all natural tourmaline. It is known for its strong pyroelectric and piezoelectric properties, meaning it can generate an electrical charge when heated or subjected to pressure. Historically, schorl was used in Europe by charcoal burners and associated with protecting against evil.

How to Identify in the Field: Look for black, prismatic crystals (often with visible striations running lengthwise) in pegmatites, granite, and metamorphic rocks. Its hardness (scratches glass) and lack of cleavage are distinguishing features. Common Locations: Found worldwide, with significant deposits in Brazil, Pakistan, Afghanistan, the USA (Maine, California), Australia, and various parts of Africa. Tips for Collectors: Seek out well-formed crystals, especially those with distinct striations. Larger, intact crystals are more valuable. Be aware that it can sometimes be confused with other black minerals like obsidian or hornblende, but its crystal habit and hardness differentiate it.