170 



PHYSIOGRAPHY. 



Dolomite. 



DOLOMITE. Macrotypous Lime-Haloide . 

 Primary form. Rhomboid. PonP=106 15'. 

 Secondary forms. 



1 . An acute rhomboid of 79 36' from Gotha in Saxony. 



2. One still more so, of 66 7', from Hall, Tyrol. 



Fig. 161. 



3. The same, having its summits sur- 

 mounted by three pyramidal faces of 

 the primary rhomboid, whose apices 

 are replaced by tangent planes, as in 

 the annexed figure. 



Cleavage, parallel with the primary rhomboid, perfect, 

 with traces of a cleavage at right angles to the vertical axis. 

 Fracture conchoidal. Surface, faces m streaked parallel 

 to the edges of combination with P. The rest of the faces 

 generally smooth, and of nearly the same physical quality. 



Lustre vitreous, inclining to pearly in several varieties. 

 Color white, seldom pure, generally inclining to red or 

 green. Various shades of red, among which is a fine rose- 

 red. Also green, brown, grey, black, very often owing to 

 foreign admixtures. Streak, greyish-white. Semi-trans- 

 parent . . . translucent. 



Brittle. Hardness = 3-5 ... 4-0. Sp. gr. =2-884, a 

 greenish white cleavable variety, from Mexico. 



