I acicular or needle arragonite."' 205 1. Very acute double six-sided pyramid, in which the lateral planes of the one are set on the lateral planes of the other. Sometimes two opposite planes are broader than the others, and the pyramid ends in a line. 2. Acute double six-sided pyramid truncated on the extremities. 3. Acute double six-sided pyramid, rather flatly acu minated with three planes, which are set on the al ternate lateral edges; or flatly acuminated with four planes, which are set on the opposite lateral edges. It sometimes happens, that two opposite acuminating planes become so large in comparison of the others, that the pyramid appears to be bevel led at the extremities. These pyramids sometimes approach to the prismatic form, sometimes to the acicular, which latter passes into the capillary. The pyramidal crystals are sometimes scopiformly ag gregated ; and the acicular crystals are scopiformly and stellularly aggregated. The lateral planes of the crystals are transversely streaked. Kxternally the lustre is shining or glistening, and vi treous, slightly inclining to pearly : internally the lustre ls splendent, and is vitreous, inclining to resinous. The fracture is stellular or scopiform radiated, and fi brous : the cross fracture small and fine-grained uneven, w hich sometimes inclines to splintery, sometimes to con- c hoidal. The fragments are indeterminate angular, and rather sharp-edged. It is translucent and transparent. It is semi-hard. it