294 DESCRIPTIONS OF MINERALS. 
easily to a white enamel. Decomposed by hydrochloric acid, 
and the solution gelatinizes on evaporation. 
Diff. Vhe alteration this species undergoes on exposure 
to the air at once distinguishes it. This result may be 
prevented with cabinet specimens, by dipping them into a 
solution of gum arabic. 
Obs. Found in the veins and cavities of trap rocks and 
also in gneiss, porphyry. Occurs at the Faroe Islands ; Kil- 
patrick Hills, near Glasgow ; Disko, Greenland ; St. Goth- 
ard, Switzerland ; Peter’s Point, Nova Scotia; Phippsburg, 
Me. ; Charlestown syenite quarries, Mass. - Bergen Hill, 
IN: J. the Copper region, Lake Superior, and Isle Royale. 
Apophylilite. 
Dimetric. In square octahedrons, prisms, and tables. 
Cleavage parallel with the base highly perfect. Massive 

and foliated. Color white or grayish ; sometimes with a 
shade of green, yellow, or red. Lustre of O pearly: of the 
other faces vitreous. Transparent to opaque. H.=4°5-5. 
G.=2-3-2-4. 
Composition. A silicate of calcium and hydrogen com- 
bined, with potassium fluoride and water, of the for ea 
(4H, $Ca) O,; Si + 4KF+ gaq=Silica 52°97, lime 24-42, 
potash 5°20, water 15°90, fluorine 2°10=100°89. B.B. exfo- 
hates, colors the flame violet (owing to the potash), and 
fuses very easily to a white enamel. In the closed tube 
yields water which has an acid reaction. Decomposed by 
hydrochloric acid with the separation of slimy silica. 
HE, el AS Sree ei a 
