10 



PROCEEDIjSTGS of the NATIOISrAL MUSEUM 

 Table 9. — Analysis of metarossite 



VOL. 72 





Natural 



Pearly 



Ratios 



Theoretical 



CaO.VsOs. 



2H2O 



Water (H2O) 



Lime (CaO) 



Magnesia (MgO) 



Vanadic oxide (¥205), 

 Insoluble __ _. __ _ 



13. 56 



20. 04 



0. 10 



64.08 

 2. 72 



14.08 



19.60 



0. 13 



64.20 



2.48 



786 

 362 



360 



2X1.088 

 1 X 1. 003 



1X0. 997 



13. 14 

 20. 44 



66. 42 





100. 50 



100. 49 



Metarossite is a hydrous calcium vanadate of the formula 

 CaO.V2Og.2H2O. It differs from rossite in its lesser hydration, that 

 mineral being the similar compound with four molecules of water. 

 If rossite is left exposed to the air it gradually becomes lighter in 

 color, loses its vitreous luster, and passes over into metarossite, still, 

 however, retaining its platy structure. If metarossite is dissolved 

 in water and allowed to crystallize, rossite separates out, but the 

 glassy crystals so obtained gradually pass over into the metarossite 

 again. It was at first thought that this change of the higher hydrate 

 to the lower one was continuous, similar to the changes in hydration 

 in other platy minerals, notably carnotite, autunite, etc. There are 

 several facts, however, that point to the existence of two distinct 

 hydrates. First, there is the occurrence of rossite as sharp residual 

 kernels in the metarossite without any suggestion of gradation ; and, 

 secondly, the two analyses made upon separate lots of material agree 

 satisfactorily with each other and very well with the theoretical 

 values for the dehydrate. 



CRYSTALLOGRAPHY 



Contributed Jyy William F. FosJiag 



No measurable crystals of metarossite were found, although on one 

 specimen a crust of the vanadate showed projections resembling 

 crystals. They were too imperfect, however, to be measured or to 

 even suggest the symmetry of the crystals. 



PHYSICAL AND OPTICAL PROPERTIES 



Contributed hi; William F. Foshag 



Metarossite is light yellow in color (Martius yellow, Eidgway) 

 and has a dull pearly luster. It is soft and friable and can be easily 

 crushed between the fingers. Due to its decided platy cleavage 



