This remakable mineral occurs imbedded in Pearlstone^* and bears a great resemblance to some of those opaque concretions so common in green glass or slag that has been slowly cooled, and has probably a similar origin. It consists of balls and veins that seem to be a scries of balls connected together, with mamillated surfaces; it breaks into angular fragments with flat dull surfaces diverging irregularly from the centres of the balls; the lustre is like that of coloured wax, the veins and some of the balls have a crust of a darker colour than their insides, and their fissures arc often filled up with a white crust. The hardness is about equal to that of Quartz, but it is more brittle; it is nearly infusible.

It is more readily decomposed by exposure to the weather, than even the Pearlstone in which it is imbedded, forming a gritty powder.

The specimens figured, shew a considerable variation in the size of the balls, the lower one is in a decomposing state. They arc from Siebenbirgen in Transylvania, it is said to be found in Iceland.