212 



Fluor. 



Compound Varieties. Twin-crystals. Face of com- 

 position parallel to one of the faces of the octahedron ; the 

 individuals having one of their axes parallel, are continued 

 beyond the face of composition, and particles of the one are 

 observed formed upon the faces of the other. See annexed 

 figure. 



Fig. 205. 



Implanted globular shapes, rare : surface drusy, composi- 

 tion columnar. Massive : composition granular, the individ- 

 uals being of various sizes ; if the composition be impal- 

 pable, its fracture becomes flat conchoidal and splintery, 

 the surface of fracture being scarcely glimmering. Mass- 

 ive varieties are also sometimes composed of columnar par- 

 ticles, generally of considerable size, seldom thin or di- 

 verging, but very often forming a second curved lamellar 

 composition. The faces of composition are sometimes ir- 

 regularly streaked, more generally uneven and rough. 



1. Before the blow-pipe, it decrepitates, and becomes phosphorescent, 

 but loses its color and melts at last into a rather opake globule. It phos- 

 phoresces likewise, if thrown upon ignited charcoal or heated iron. Sev- 

 eral varieties which exhibit this property in particularly bright green 

 colors, have been called Chlorophane or Pyro-smaragdus. If expo- 

 sed to a high degree of temperature, they lose the property ef again 



