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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.
In the line rock, this black tourmaline occurs as tiny prismatic crystals.
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.