358 PHYSIOGRAPHY, CLASS n. 



Fundamental form. Hexahedron. Vol. I. Fig. 1. 

 Simple forms. (P) Vol. I. Fig. 13. ; ~ (*) 



Vol. I. Fig. 14. 

 Char, of Comb. Semi-tessular with inclined faces. 



Combination. -. -. Fig. 158. 



Cleavage, traces of the octahedron. Fracture un- 

 even. Surface, of one of the tetrahedrons smooth, 

 a little rounded and uneven, sometimes streaked 

 parallel to its edges, of the other rough but even. 



Lustre vitreous, inclining to resinous. Colour 

 wax-yellow, inclining to honey-yellow and yellow- 

 ish-brown, or also to siskin-green. Streak white. 

 Translucent on the edges. 



Hardness = 6-0 ... 6-5. Sp. Gr. = 3-100, of a 

 very small quantity. 



OBSERVATIONS. 



,1. According to VOGEL, it consists of 



Silica 3950. 



Alumina 15 -65. 



Oxide of Iron 3775. 



Oxide of Manganese 3'75. 



Lime 0-50. 



Before the blowpipe upon charcoal, it melts in the re- 

 ducing flame with effervescence into a globule of almost the 

 same colour as the mineral. In the oxidating flame the 

 colour becomes dark, and the fusion more difficult. With 

 borax it yields a transparent glass, often coloured by man- 

 ganese. 



2. Tetrahedral Garnet has been hitherto found only at 

 S^hwarzenberg in Saxony, in beds in gneiss. It is accom- 

 panied with dodecahedral Garnet-blende, rhombohedraj 



