quartzoid

\\ˈkwȯrtˌsȯid\ noun (-s)

: a crystal that is common with quartz and consists of a combination of the hexagonal prism and dipyramid

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ˈquartzoid

[f. as quartz + -oid.]

A crystal having the form of a double six-sided pyramid.

Webster cites Dana. Dana Man. Min. (ed. 4) 47.