polyedral

A red, a dull yellow, and a purplish sand-stone, are also found in small pieces; and pretty large lumps of semi-transparent quartz, disposed irregularly in polyedral pyramidal crystals of long shining fibres.

A General History and Collection of Voyages and Travels — Volume 15 Forming A Complete History Of The Origin And Progress Of Navigation, Discovery, And Commerce, By Sea And Land, From The Earliest Ages To The Present Time Robert Kerr 1784