122 LIMESTONE FAMILY. The fracture is foliated, sometimes straight, some times curved, and the folia have a single distinct cleav age. It is opaque ; feebly translucent in thin pieces. It occurs in large and small granular distinct concre tions. It soils slightly, with glimmering dusty particles. It is soft. It is sectile. It is not particularly heavy. Chemical Characters. The same as the other subspecies. Geognoslic Situation. It occurs in the first fleets! limestone, and first fleet* gypsum. According to Friesleben, it appears to be geo- gnostically allied to selenite; and although it differs from that mineral in colour, transparency, lustre, sectility, feel, and effervescence with acids, yet it passes into it, and al so into slaty aphrite, sometimes by simple gradations, sometimes by intermixture of the two minerals ; and large lenticular crystals of selenite occur, which are pure at the edges, become gradually more opaque towards the centre, and in the centre are pure sparry aphrite. Geographic Situation. It occurs in Thuringia. Observations. It was first described and named by Friesleben, in his Geognostical Contributions. 4. Agaric
