Black Tourmaline

Hardness: 7-7.5 (Mohs scale), Color: Typically opaque black, sometimes dark blue or brownish-black. Luster: Vitreous to resinous. Crystal Structure: Trigonal, commonly forming elongated prismatic crystals with vertical striations. Cleavage: Poor to indistinct. Specific Gravity: 3.1-3.3.

Black tourmaline forms in igneous and metamorphic rocks, particularly in granites, pegmatites, and high-temperature hydrothermal veins. It crystallizes from boron-rich magmas or solutions. Its geological age varies widely depending on the specific rock formation it's found in, ranging from Precambrian to more recent eras.

Black tourmaline is widely used as a gemstone, though often opaque. It is valued in metaphysical and healing practices for its purported protective and grounding properties. In industry, it can be used in pressure gauges due to its piezoelectric properties, though synthetic alternatives are more common for this purpose. It is also collected by mineral enthusiasts.

Black tourmaline, or schorl, is the most common variety of tourmaline, accounting for over 95% of all natural tourmaline. The name 'tourmaline' comes from the Sinhalese word 'turmali', meaning 'mixed colored stones', although schorl is almost exclusively black.

Black tourmaline is identifiable in the field by its distinct black color, prismatic crystal habit with prominent striations running parallel to the long axis, and its hardness. It can often be found in association with quartz and feldspar in granitic environments. Common locations include Brazil, Africa (e.g., Namibia, Tanzania), Pakistan, and the United States (e.g., Maine, California). Tips for collectors include looking for well-formed crystals in pegmatite veins.