208 DESCRIPTIONS OF MINERALS. 
With the exception of the calcium nitrate, none of the 
native salts of ime are soluble in water except in small 
proportions. 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 d. , 
F'luorite.—Fluor Spar. Calcium Fluoride. 

Isometric. Cleavage octahedral, perfect. Commonly in 
erystals ; rarely fibrous; often compact, coarse or fine gran- 
ular. Figures 1 to 4 represent common forms. 

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 subtranslucent. H=4. 
G. =3-3°25. Brittle. 
Composition. Ca ¥,=Fluorine 48°7, calcium 51:°3=100. 
Phosphoresces when gently heated in the uark, 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 

