104 



PHYSIOGRAPHY. 



Calcareous Spar. 



Cleavage parallel to the primary rhomboid, easily ob- 

 tained, even and highly perfect. Fracture, perfectly con- 

 choidal, but difficult to be obtained. 



Surface generally even : rarely, curved faces appear in 

 certain rhomboids and pyramids. 



Lustre vitreous. The lustre of c is sometimes pearly. 

 Color white, prevalent. Also different shades of grey, red, 

 green, yellow ; all of them pale. Dark brown and black 

 colors owing to foreign admixtures. Streak greyish white. 

 Transparent . . . translucent ; double refraction very con- 

 siderable, and easily observed. 



Brittle. Hardness =3-0. Sp. gr. =2*721, a transpa- 

 rent crystal. 



Compound Varieties. Twin-crystals. 

 Fur. 116. 



Fig. 117. 



Fig. 119. 



