GLAUBER SALT. 317 It occurs in the form of mealy efflorescences; in crusts, seldom stalactitic, small botryoidal, reniform ; and crys tallised, 1. In acicular crystals*. 2. In six-sided prisms, more or less flatly acuminated by three planes, which are set on the alternate edges or planes. The acicular crystals are small, the prisms middle- sized, and so grown together, that they are with diffi culty distinguishable. Internally it is shining, and the lustre is vitreous. The principal fracture of the crystallised varieties is foliated, with a threefold cleavage : the cross fracture is small conchoidal; that of others fine-grained uneven. When decomposed, the fracture is earthy. The fragments are indeterminately angular, and blunl- edged. It occurs sometimes in small and fine granular distinct concretions. It is soft; the earthy varieties are friable. It is brittle. It is easily frangible. Its taste is first cooling, and then saline and bitter. Chemical Characters. Hefore the blowpipe, it is affected in the same manner as Epsom salt; but its solution does not, like that of Epsom salt, afford a precipitate with an alkali. Constituent * The primitive form of Glauber salt is an octahedron.