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258 BOTLACITE FAMILY. Internally it is shining, inclining to glistening, and the lustre is resinous. The fracture is small grained uneven, which sometimes approaches to splintery, and small conclioidal *. The fragments are indeterminate angular, and rather sharp-edged. It occurs in large, coarse, and small angulo-granular distinct concretions, which are easily separable, and some times approach to the prismatic and wedge shape.,, It is generally translucent, and sometimes transparent. It is semi-hard ; it scratches glass with difficulty. It is very brittle. It is difficultly frangible. Specific gravity, 2.980, Klaproth. Chemical Characters. When exposed to the flame of a candle, it becomes opaque, and may then be easily rubbed down between the fingers. Before the blowpipe, it intumesces into a milk-white coloured mass, and then melts into a globule of a pale rose colour. Constituent Parts. Silica, 30.50 Silica, 37.60 Lime, 35.50 Lime, 34.00 Boracic Acid, 24.00 Boracic Acid, 21.67 Water, 4.00 Water, 5.50 Trace of Iron and Loss, 1.17 Manganese. 100.00 100.00 Vauquelin, in Lucas* Klaproth, Beit. Tub. Mcth. II. 7*' b. iv. s. 359. Gcognost* c * Ilausmann is of oji ; nion, that a double cleavage occur*, in which tllf cleavages are parallel with the aides of the oblique four-sided prinu.