110 



Mr. H. E. Eoscoe on 



[June \o, 



of San Trancisco, with the following statement : — " I discovered it in 

 a gold-mine, and it serves as the matrix for the gold. It occurs in small 

 bunches, filling cavities in a schistose porphyry." 



The mineral occurs in radiating and foliated talc-like masses, greenish 

 grey in bulk, and light greenish yellow when seen in fragments, forming 

 a grey powder. Its lustre is subvitreous to fatty. In mass it is 

 opaque, but is translucent in thin splinters. Its hardness is about 

 equal to that of talc ; its specific gravity is 2-902. 



BlowpiiDe reactions. — "When heated in thin splinters the mineral fuses 

 easily to a black non-magnetic bead. In a closed tube a little water is 

 given off. With borax and microcosmic salt the reactions of vanadium 

 and silica are obtained. It is only partially attacked by acids. 



Composition. — Two complete analyses of the mineral have been made 

 with the following results : — 





I. 



II. 



Mean. 





41-25 





41-25 



Vanadium pentoxide 



28-85 



28-36 



28-60 





14-34 



13-94 



14-14 





1-04 



1-23 



1-13 



Manganese sesquioxide . . 



1-45 



•85 



1-15 



Lime 



-61 



•62 



•61 





1-96 



2-06 



2-01 





8-25 



8-87 



8-56 





•72 



'92 



•82 





•94 



1-22 



1-08 





2-12 



2-42 



2-27 





101-53 





101^62 



The following formula approximately represents the composition of 

 this mineral, a portion of the aluDiina being replaced by the sesqui- 

 oxides of iron and manganese, and a portion of the poiassium oxide by 

 lime, magnesia, and soda : — 



2 (Al, O3 . Y,Og) -I- 2 K,0 . 9 Si + IT,0, 

 or 4 Al VO, -f Si^O,,"-!- H,0. 



Thus we have : — 





Calculated. 



Found. 





41-18 



40-38 





27-63 



28-00 





15-59 



15-32 





14-24 



15-24 





1-36 



1-06 





100-00 



100-00 



Vanadium and aluminium salts cannot be separated by fusion with 

 sodium carbonate and subsequent precipitation by ammonium chloride, 

 as some of the alumina is thrown down as aluminium vanadate together 

 with the ammonium vanadate. 



