306 T. L. Walker — Tungstite and Meymaeite. 



eral apparently results from the alteration of wolframite. 

 Having determined by the aid of the pycnometer the specific 

 gravity of the aggregate as a whole and later of the part insol- 

 uble in ammonia and knowing the relative proportions of the 

 soluble and insoluble constituents, it is simple to calculate the 

 specific gravity of the yellow soluble constituent. In this way 

 the density has been found to be 5 - 517, hardness 2'5, luster 

 resinous, pearly on the one perfect cleavage. In thin section 

 the mineral is seen to be golden yellow, in transmitted light, 

 but not perceptibly pleochroic. The index of refraction is less 

 than that of Canada balsam since the mineral in thin section is 

 smooth-surfaced. Examined between crossed nicols the polari- 

 zation colors are brilliant, indicating fairly low double refrac- 

 tion. As the mineral is very cleavable in one direction 

 numerous cleavage plates are torn loose in the mounting, and 

 these being oriented so that their cleavage plane is that of the 

 mount, give in convergent light biaxial interference figures. 



Although there are numerous druses lined with tiny crystals 

 none of them was large enough for study on the goniometer. 

 All that we know of the ciwstallography of this mineral 

 depends upon two observations : the mineral possesses one per- 

 fect cleavage and these cleavage plates exhibit biaxial inter- 

 ference figures. Since in this case the acute bisectrix is at 

 right angles to the cleavage we may conclude that the mineral 

 may be rhombic and the cleavage pinacoidal, or it may be 

 monoclinic with the cleavage parallel to the plane of symme- 

 try. Later it may be possible to secure crystals large enough 

 to settle this question definitely. 



Chemical characters. — Since both tungstite and meymaeite 

 are said to be soluble in ammonia and sodic hydroxide, the 

 powdered mineral was treated with warm caustic soda, and the 

 residue washed and dried at 110° was found to make up only 

 13-52 per cent of the whole. In this way it was possible to 

 consider (from a chemical point of view) the specimens as 

 made up of two parts — one soluble in alkali corresponding to 

 tungstite or meymaeite, and an insoluble portion made up, 

 according to physical and chemical examination, of wolframite, 

 limonite and scheelite. 



The result of a complete analysis was as follows : 



WO 86-20$ 



CaO° -54 



FeO* 1-21 



Fe,0, 4-14 



H 2 0; 772 



Total 99-81$ 



* The condition of the iron was not determined — that portion necessary to 

 form wolframite with the balance of the tungstic acid has here been 

 expressed as FeO. 



