FL UOR-SPAR CAL C-SPAR. 



105 



Fluor-Spar. 



Though by no means so common a matrix as quartz, it 

 often forms or is mixed with the gangue of copper, lead, or 

 silver-bearing lodes. Is usually purple, sometimes yellow, 

 white, or green, and occasionally blue. If a piece be heated 

 in a dark place, a phosphorescent light may be noticed. 

 Fluor-spar might be mistaken for a precious stone; its 

 softness, however, is a distinguishing feature. 



Crystallizes most commonly in cubes, octahedra, &c. 

 Crystals are transparent or translucent. H. 4; S.G. 

 3-14 to 3-18. Is brittle. When heated in a closed tube, 

 decrepitates and phosphoresces. 



Gives opaque beads when heated with borax and micros- 

 mic salt before B.F. If melted in a tube with microsmic 

 salt it gives off vapour of hydrofluoric acid, which corrodes 

 the glass. 



If the powdered mineral be dissolved in sulphuric acid, 

 the gaseous acid will corrode glass, and even siliceous 

 stones. Blue John is a name given by Derbyshire miners 

 to a blue fluor-spar. Composition : lime, 51 ; fluorine, 48. 



Calc-Spar (carbonate of lime). 



Generally transparent or translucent. Crystallization 



FIG. 56. 



FIG. 57. 



COMMON FORMS OF CALC SPAR. 



FIG. 58. 



rhombohedral, &c. Some common forms being as above. 

 The faces are sometimes very brilliant. H. 3 ; S.G. 

 2'5 to 2 '8. Is colourless, topaz, or honey yellow, grey rose, 

 violet, &c. 



Is infusible before the B.F., gives a very bright light, 

 and is eventually reduced to a quicklime. It effervesces 

 when acted on by an acid. 



