sillimanite

noun
sil·​li·​man·​ite | \ ˈsi-lə-mə-ˌnīt How to pronounce sillimanite (audio) \

Definition of sillimanite

: a brown, grayish, or pale green mineral that consists of an aluminum silicate in orthorhombic crystals often occurring in fibrous or columnar forms

First Known Use of sillimanite

circa 1830, in the meaning defined above

History and Etymology for sillimanite

Benjamin Silliman †1864 American geologist

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