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A glassy pink, green, violet, or blue aluminum borosilicate mineral, Al8BSi3O19OH, used in spark-plug ceramics and as imitation lapis lazuli.
[French, after Eugène Dumortier, 19th-century French paleontologist.]
(Minerals) a hard fibrous blue or green mineral consisting of hydrated aluminium borosilicate. Formula: Al7O3BO3(SiO4)3
[C19: named after Eugène Dumortier, 19th-century French palaeontologist who discovered it]