120 LIMESTONE FAMILY. 2. According to Mohs, Tabular-Spar and Slate-Spar are connected, by means of this species, with Agaric Mi neral and Chalk, and the transition from Chalk into Limestone is evident; so that thus the whole of these species form nearly a natural group. Second Subspecies. Slaty Aphrite. Schaumschiefer, Friesleben. Schaumschiefer, Friesleben, Gcognostiche Beitr'age, b. ii. s. 232 External Characters. Its colours are snow-white, passing into yellowish, reddish, and silver white. It occurs massive, seldom coarsely disseminated. It is strongly glimmering, sometimes approaching to glistening, even to shining; and the lustre is pearly, which sometimes passes into semi-metallic. It is slaty in the great, but undulating curved foliated in the small. It splits very easily into extremely thin tabular frag ments. It is opaque; only very feebly translucent in the thinnest folia! It soils pretty strongly, with scaly particles. It is very soft. It feels soft, and rather silky. It is flexible in thin plates. * It is light. Chemical