THE NONMETALLIC MINEBALS. 



391 



6. TRIPHYLITE AND LITHIOPHILITE. 



These are names given to phosphates of iron, manganese, and lithium, 

 and which pass into one another by insensible gradations through 

 variations in the proportional amounts of manganese protoxide, the 

 triphylite containing from 10 to 20 per cent of this oxide, while the 

 lithiophilite contains twice that amount. The comparative composition 

 of extreme types is shown below: 



Triphylite is a gray to blue-gray mineral in crystals and coarsely 

 cleavable masses of a hardness of 4.5 to 5 of Dana's scale, and specific 

 gravity of 3.42 to 3.56. 



Lithiophilite differs mainly in color aside from composition as 

 above noted being of a pink to clove-brown hue. Both minerals 

 may undergo a darkening in color, becoming almost black through a 

 higher oxidation and l^d ration of the manganese protoxide. This 

 feature is best shown in the lithiophilite from Branchville, Connecticut, 

 (Specimen No. 62583, U.S.N.M.) 



Occurrence. These minerals occur chiefly in granitic veins, associated 

 with spodumene and other lithia bearing minerals, as at the localities 

 above mentioned. Peru, Hebron, and Norway, Maine; Keityo, Fin- 

 land, etc. 



IX. NITRATES. 



There are three compounds of nitric acid and a base occurring in 

 nature in such quantities and of sufficient economic importance to 

 merit attention here. These are (1) the true niter or potassium nitrate 

 (KNO 3 ), (2) soda niter or sodium nitrate (NaNO 3 ), and (3) nitrocal- 

 cite, a calcium nitrate (CaN 2 O 6 ). All are readily soluble in water, and 

 hence found in any quantity only in arid regions or where protected, 

 as in the dry parts of caves. 



1. NITER, POTASSIUM NITRATE. 



Composition KNO 3 ,=nitric anhydride, 53.5 per cent; potash, 46.5 

 per cent. Hardness, 2; specific* gravity, 2.1; color, white, subtrans- 

 parent. Readily soluble in water. Taste, saline and cooling. Defla- 

 grates vividly when thrown on burning coals and colors the flame 

 violet. 



The mineral occurs in nature mainly in the form of acicular crystals 

 and efflorescences on the surface or walls of rocks and scattered in the 

 loose soil of limestone caves and similar dry and protected places. 



