Definition of tourmaline in English:

tourmaline

noun

  • [mass noun] 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.

    • ‘It consists of clasts of angular to rounded quartz, plagioclase, tourmaline and rock fragments, up to 3 mm in diameter.’
    • ‘The mineral assemblage comprises quartz, K-feldspar, albitic plagioclase, white mica, apatite, tourmaline and garnet.’
    • ‘Inclusions of quartz, tourmaline, apatite, and muscovite crystals have been described.’
    • ‘After quartz and microcline, tourmaline is arguably the next most abundant mineral found in the miarolitic cavities.’
    • ‘In the line rock, this black tourmaline occurs as tiny prismatic crystals.’

Origin

Mid 18th century: from French, based on Sinhalese tōramalli carnelian.

Pronunciation:

tourmaline

/ˈtʊəməlɪn//ˈtʊəməliːn/