A typically black or blackish mineral that occurs as prismatic crystals in granitic and other rocks. It consists of a boron aluminosilicate and has pyroelectric and piezoelectric properties.
- In the line rock, this black tourmaline occurs as tiny prismatic crystals.
- The mineral assemblage comprises quartz, K-feldspar, albitic plagioclase, white mica, apatite, tourmaline and garnet.
- It consists of clasts of angular to rounded quartz, plagioclase, tourmaline and rock fragments, up to 3 mm in diameter.
Mid 18th century: from French, based on Sinhalese tōramalli 'carnelian'.
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Line breaks: tour¦ma|line
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