344 SILICATES. which the half form e' appears, the analogous pole. Gene rally, but not invariably, the former is the end at which the edges formed by the faces r are directed towards the faces of the hemihedral form b\ as in fig. 361; the latter that at which the edges formed by the intersections of the faces of t are directed to the intersections of the faces, as in fig. 362; figs. 361, 362, representing the opposite ends of the same crystal. Before the blowpipe black tourmaline from Kiiringbrieka melts with intumescence, and with borax and salt of phosphorus yields the reactions of iron and silica; tourmaline from Bovey melts into a black slag. The red and light green tourmalines containing lithia and soda intumesce, but do not melt. With soda they yield the reaction of manganese. With fluor spar and bisulphate of potash they all impart a green colour to the flame. After fusion, but not before, is almost completely decomposed by concentrated sulphuric acid. Analyses by Rammelsberg of yellow and brown tourmaline containing but little iron and the largest quantity of magnesia, and in which the proportions of oxygen in the bases it,*» and the acids, are nearly as the numbers l, 3, 5. a from Gouver- neur in New York, h from Windisch-Kappel in Carinthia, c from Eibenstock in Saxony, d from Orford in New Hampshire, e from Monroe in Connecticut,/from the Zillerthal in the Tyrol:— a b C d e / G 3'049 3-035 3-034 3-008 3-068 3-054 Fluorine . . . 2-28 2-10 2-61 2-50 2-38 2-50 Phosphoric acid . trace 0‘12 — 0-24 0-24 Silica 38-85 38-08 37-83 38-33 39 01 37-1*4 Boracie acid . . 8‘2o 9-39 8-88 9-86 9-04 8-58 Alumina.... 31-32 34-21 30-86 3315 31-18 33-64 Red oxide of iron . 1-27 143 4-86 3-07 3-44 2’79 Protoxide of iron . — — 0-12 0-98 0-37 Magnesia . . . 14-89 11-22 11-62 10-89 9’90 10 - 46 Lime 1-60 0 61 0-88 0-77 1-81 0-98 Soda 1-28 2-37 2-27 1 1-82 2-13 Potash .... 0-28 0-47 0-30 J 1*52 044 0-37 In analysis b the contains iln. Analyses of black tourmaline containing a mean proportion of iron and magnesia, and in which the proportions of oxygen in the bases it, it, and in the acids are nearly as the numbers L 4, e. ff from Gothaab in Greenland, h from Texas in Lan caster County, Pennsylvania, i from St. Gotthardt, k from