Dolomite family. It occurs massive, disseminated, and crystallised in rhombs, which are sometimes rounded, or truncated on the edges. The crystals are middle-sized and small; the surface is sometimes smooth, sometimes rough, and either shining or glimmering. Internally the lustre is splendent, between vitreous and pearly *. The principal fracture is foliated, with a threefold ob lique angular cleavage: the alternate angles of which measure 106° 15' and 73° 46'; the cross fracture imper fect conchoidal ■}•. The fragments are rhomboidal. It is semi-hard ; harder than calcareous-spar, or brown- spar. It is easily frangible. It is brittle. Specific gravity, 2.880, 3.000. 2.8901, Murray *. Chemical Characters. Before the blowpipe it is infusible, without addition i even when pounded, it effervesces but feebly ; and dis solves slowly in muriatic acid. Constituent # The lustre in general is stronger than that of calcareous-spar.—Bom- non. Dr Wollaston. $ Newton-Stcwart, Galloway.
