208 



DESCRIPTIONS OF MINERALS. 



With the exception of the calcium nitrate, none of the 

 native salts of lime are soluble in water except in small 

 rn-oportions. They give no odor, and no metallic reaction 

 before the blowpipe ; but they tinge the flame red, and 

 many of them give up a part of their acid constituent, and 

 become caustic and react alkaline. The specific gravity is 

 below 3*2, and hardness not above 5. 



Fluorite. — Fluor Spar. Calcium Fluoride. 



Isometric. Cleavage octahedral, perfect. Commonly in 

 crystals ; rarely fibrous ; often compact, coarse or fine gran- 

 ular. Figures 1 to 4 represent common forms. 



1. 



^^\ 



-// ^ 



k 





U 



J 





G 



^-•••* 





J 



m& 



a 



w 



Colors usually bright ; white, or some shade of light 

 green, purple, or clear yellow are most common ; rarely 

 rose-red and sky-blue ; colors of massive varieties often 

 banded. Transparent, translucent or subtraiislucent. H = 4. 

 G.=3-3-25. Brittle. 



Composition. CaF 2 = Fluorine 48*7, calcium 51 -3 = 100. 

 Phosphoresces when gently heated in the dark, affording 

 light of different colors ; in some varieties emerald-green ; 

 in others, purple, blue, rose-red, pink, or orange. B.B. 

 decrepitates, and ultimately fuses to an enamel, which pos- 

 sesses an alkaline reaction ; pulverized and moistened with 

 sulphuric acid, hydrofluoric acid gas is given off which cor- 

 rodes glass. The name Chlorophane has been given to the 

 variety that affords a bright green phophorescence. 



Diff. In its bright colors, fluorite resembles some of the 

 gems, but its softness and its easy octahedral cleavage when 

 crystallized at once distinguish it. Its strong phosphores- 

 cence is a striking characteristic; and also its affording 



