AET. 11 



EOSSITE AND METAKOSSITE FOSHAG AND HESS 



Sufficient material in the form of hard, glassy cores of rossite 

 could be selected from the more flaky mineral and cleaned by rubbing 

 the soft metarossite off. The rossite could not be completely puri- 

 fied by this means, but the sample analyzed carried only a small 

 percentage of the metarossite and a few per cents of sand grains 

 from the inclosing sandstone. For a second analysis a quantity of 

 the metarossite was recrystallized and the clear, glassy crystals so 

 obtained used. 



Water was determined as loss on heating. Since the mineral 

 fused easily, a low temperature was sufficient to accomplish the com- 

 plete expulsion of the water. Actually most of the water was driven 

 off at a temperature of 120° C. As the dehydrated mineral is very 

 slowly soluble in water, another portion was taken for the other 

 constituents. The mineral was dissolved in hot water, the insoluble 

 matter filtered off, and the vanadium precipitated as mercuric vana- 

 date and ignited to the oxide. Lime and magnesia were determined 

 in the usual manner. Constituents precipitated by hydrogen sul- 

 phide in acid solution (Pb, Cu, Mo, etc.) were found to be absent. 

 Iron and phosphorus could not be detected. The results follow : 



Table 1. — Analysis of rossite 



Constituent 



Natural 

 glassy 



Recrystal- 

 lized 



Ratios 



Theoretical 



CaO.VsOs.- 



4H3O 



Water (H2O) 



Lime (CaO) 



Magnesia (MgO)__ 

 Vanadic oxide 

 (V2O5) 



22.90 



18. 00 



0. 14 



58.00 

 1.60 



22.59 

 18.48 



1,255 

 330 



323 



4X0.963 

 1X1. 012 



1X0.990 



23.22 

 18.07 



58.71 



58.92 



Insoluble. 







100. 64 



99.99 



Rossite is therefore a simple hydrous calcium vanadate. Its com- 

 position is expressed by the formula CaO. VgOs- ^HgO. In the last 

 column of Table 1 the theoretical composition for this compound is 

 given. 



CRYSTALLOGRAPHY 



Contn^uted 'by William F. Foshag 



GKNBEAL 



None of the specimens of rossite show any crystallographic forms. 

 The mineral, however, is soluble in water, and material suitable for 

 goniometric measurements can easily be obtained by recrystallization. 

 The habits of crystals obtained in this manner were all very similar, 

 and repeated recrystallizations under various conditions failed to 



