Dipyre

Dipyre. has hitherto been found only in one place, where it was discovered so long ago as 1786, by Lelièvre and Gillet Laumont, on the right hank of the gave de Mauléon, in the Hautes Pyrenees, imbedded in a grey clayey earth, accompanied by green or white Talc and cubical Iron pyrites. It is either in very small prismatic crystals that are scattered through the gangue, or in small masses of a fibrous structure. The crystals are rectangular prisms, with two or four of their vertical edges truncated, so as to produce six or eight-sided columns: the ends appear to be uneven, at least I have not met with any that exhibit even faces. They are imperfectly transparent in some parts, and opaque in others, with a weak lustre, wherefore, they have a slightly pearly aspect: Haüy describes the longitudinal fracture as displaying laminæ parallel to all the eight sides of the prism; the cross fracture is conehoidal. It is hard enough to scratch glass, but very brittle; the massive variety (see the lower fig.) has sometimes a loose structure. When slightly heated it emits a faint light; before the blow-pipe it readily melts with intumescence into a semitransparcnt globule. The specific gravity is 2.630.