PHYSIOGRAPHY. 227 



Tautolite. 



ras formerly used in medicine, and is now employed in removing oil- 

 tains from woollen cloth. 



TANTALITE. (See Columbite.) 

 TAUTOLITE. 



Primary form. Right rhombic prism. M on M = 109 46'. 



Secondary form. The primary, having the acute angles, and 

 the acute lateral edges truncated ; the former so deeply as to pro- 

 duce a dihedral summit of 51 52'. The acute lateral edges are 

 also bevelled, the bevelling planes meeting at an angle of 86 22'. 



Cleavage, cnly in traces, and interrupted parallel to M. Frac- 

 ture conchoidal . . . uneven. 



Lustre vitreous. Color velvet-black. Streak grey. Opake. 



Hardness = 6 5 ... 7-0. Sp. gr. = 3-865. 



1. Before the blow-pipe, on charcoal, it melts to a blackish scoria, 

 which is attracted by the magnet ; with borax, it melts to a clear green 

 rlass. Hence it may be presumed to consist of silica, protoxide of iron, 

 magnesia and alumina. 



2. It is fourivl in the volcanic rocks in the neighborhood of Lake Laach 

 n Prussia. 



3. It is closely related to Peridot. 



TELLURIC BISMUTH. (See Bornine.) 



TELLURIC LEAD. 



Massive. 



Cleavages in three directions, apparently leading to the cube. 

 Lustre shining. Color, tin-white. 

 Hardness =3-0. Sp. gr. =8-159. 



1. It colors the flame of the blow- pipe blue. It melts, and is at length 

 reduced to a little button of silver, surrounded by a sublimate of telluret 

 of lead, and a yellowish brown deposit. 



2. Analysis. 

 By ROSE. 



Lead - 60-36 



Silver 1-28 



Tellurium 38-37 



3. It is found with Blende, Iron Pyrites and Telluric Silver, at the 

 mine of Sawodinski in Siberia. 



4. It approaches in its properties the Black Tellurium. 



