Cobaltiferous Sulphate of Magnesia

Sulphate of Magnesia has hithorto been found as a pulverulent crust upon the exposed surfaces of some rocks, or crystallized in brilliant spicule upon stones containing Magnesia and Iron pyrites, by the decomposition of which it has been produced; in this latter form it has occurred upon schale, in the Murlet mine near Paisley: the variety figured has been long known, and having once been called Sulphate of Cobalt, although in fact it contain but a small portion of metal, it has since been confounded with that salt, but the paleness of its colour and bitter taste readily distinguish it. It has been found only at Herrengrund in Hungary: De Born mentions a specimen of it, containing a drop of water. Haüy observes that it is found in Copper mines, and is accompanied by Quartz and Sulphate of Lime. Vauquelin determined its composition. It is probable that like most of the soluble salts that occur in mines, it is produced after the vein has been exposed to the action of the atmosphere.

From the British Museum.