pyrito-|pɪˈraɪtəʊ, ˈpaɪərɪtəʊ|combining form of pyrites, occurring in a few scientific terms. pyrito-biˈtuminousa., containing pyrites and bitumen. pyritohedron|-ˈhiːdrən, ˈhɛdrən|, pl.-hedra, Cryst.[Gr. ἕδρα side, after tetrahedron, etc.], a form of pentagonal dodecahedron, or solid contained by twelve pentagons, common in crystals of pyrite; hence pyritoˈhedrala., pertaining to or of the form of a pyritohedron. pyriˈtology[ad.mod.L. pyrītologia: see -logy], a treatise on, or the study of, pyrites.1796Kirwan Elem.Min. (ed. 2) II. 17 The Ores in which Allum owes its origin to the decomposition of Pyrites... 1st. The purely pyritous... 2d. The *Pyrito Bituminous.1868Dana Min. 62 Pyrite. Isometric; *pyritohedral... The cube..most common; the *pyritohedron..and related forms..very common. Cubic faces often striated.1895Story-Maskelyne Crystallogr. §190. 229 A remarkable combination of pyritohedron and octahedron is a not uncommon form of pyrites and cobaltite... The eight faces of the octahedron are equilateral triangles, and the twelve faces of the pyritohedron assume also a triangular form.[1725J. F. Henckel (title) *Pyritologia, oder Kiesz Historie.1757(title) Pyritologia, or a History of the Pyrites.]1828–32Webster, Pyritology, a discourse or treatise on pyrites.