adamantoid

noun (-s)

Etymology: adamant (I) + -oid

obsolete : hexoctahedron

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adamantoid Cryst.

(ædəˈmæntɔɪd)

[mod. f. Gr. ἀδάµαντος of adamant + -ειδής -form; see -oid.]

‘A form of crystal occurring in the diamond, bounded by forty-eight equal triangles.’ Dana.