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G10 FLUORIDES, CHLORIDES, BROMIDES, IODIDES. TIG. 821. TIG. 622. TIG. 623. if**', Forms and combinations, a, o, d, f m, t, ao, ad, af, am, at, ap, oe, oq, op, of, aof, aot, aod, adm, adf afm, aft, amt, ode, aodt, aodk, aodm, aomf adef admt.x. The faces a usually smooth, sometimes striated parallel to their intersections with e or t; o frequently rough; e, f k striated parallel to their intersec tions with a. Twins. Twin-face o. Cleavage, o, very perfect; d, sometimes tolerably distinct; a, traces. Fracture conchoidal, more or less perfect. Transparent...translucent. Lustre vi treous. p = 1'436. Colourless, white, grey, yellow, red, blue, green, black. Sometimes different colours appear disposed in layers parallel to the faces of some of the simple forms, and a crystal of one colour occurs imbedded in the interior of a crystal of a different colour. The colours of fluor are some times different according as they are seen by reflected or by transmitted light. Some varieties are green by transmitted light, and blue by reflected light. Streak white. Brittle. H = 4 - 0. G = 3'017...3'188. Phosphoresces when heated or broken, but loses this property when the temperature surpasses a certain limit. Before the blowpipe, in thin splinters, intumesces and melts into an opaque enamel, which in a strong heat becomes infusible and alkaline, and imparts a red colour to the flame. Beadily soluble in borax and salt of phosphorus. With gypsum, baryte or celestine melts into a clear bead, which becomes opaque on cooling. Soluble in hydrochloric and nitric acids. Is com pletely decomposed by sulphuric acid with evolution of hydro fluoric acid. CaFl, fluorine 48-63, calcium 6l - 47. Berzelius obtained 72-14 and 71'77 parts of lime from loo parts of fluor from Alston Moor and from Norberg respectively. In fluor from Derbyshire he found 0’5 per cent, of phosphate of lime. According to Kersten, many blue varieties of fluor from Freiberg and Marienberg contain small quantities of chlorine. In attached crystals, granular or fibrous masses, compact, disseminated, earthy, as the substance of petrified cyathoc- rinites. The crystals sometimes contain grains of quartz, me tallic sulphides, clay, and sometimes drops of water.
