ORDER I. OCTAHEDUAL FLUOR-HALOIDE. 71 



Compound Varieties. Twin-crystals. Axis of 

 revolution perpendicular, face of composition pa- 

 rallel to one of the faces of the octahedron ; the in- 

 dividuals, having one of their axes parallel, are 

 continued beyond the face of composition, and par- 

 ticles of the one are observed formed upon the 

 faces of the other. Fig. 128. Implanted globular 

 shapes, rare : surface drusy, composition columnar. 

 Massive : composition granular, the individuals being 

 of various sizes ; if the composition be impalpable, 

 the fracture becomes flat conch oidal and splintery, 

 the surface of fracture being scarcely glimmer- 

 ing. Massive varieties are also sometimes com- 

 pound of columnar particles, generally of consider- 

 able size, seldom thin or diverging, but very often 

 forming a second curved lamellar composition. The 

 faces of composition are sometimes irregularly 

 streaked, more generally uneven and rough. 



OBSERVATIONS. 



1. Fluor has been divided into foliated and. compact Fluor, 

 of which the first is more generally called Fluor-spar. 

 This division comprehends the simple varieties, and such 

 compound ones as consist of individuals, whose cleavage 

 can still be ascertained. The other includes those in which 

 the individuals are too small to allow cleavage to be observ- 

 ed. This division is not erroneous, but it is useless. A 

 third sub-species has been added to the former two, which 

 comprehends the earthy Fluor, or the friable varieties of 

 the species, in which the individuals have lost their con- 

 nexion, probably by decomposition. 



2. Octahedral Fluor-haloide consists of 



Lime 67-75* 



Fluoric Acid 32-25. KLAPKOTH. 



