10 PROCEEDINGS OF THE CALIFORNIA 
On Roscoelite, or Vanadium Mica. 
BY JAMES BLAKE, M. D. 
Ata meeting of the Academy in September of last year, I presented a 
specimen of a new mineral, under the name of Colomite, which I then consid- 
ered to be a mica, containing a large percentage of chromium. I had, at that 
time, made no detailed analysis of the substance, and had merely arrived at 
the conclusion that it was a chrome mica, from some superficial blow-pipe 
tests, and from its reaction with acids; knowing, also, that chromium is not 
an uncommon ingredient in micas. Subsequent to my last communication 
on the subject, Dr. Ghent, of Philadelphia, to whom a specimen of the min- — 
eral had been sent, discovered that it contained vanadium, and on his inform- 
ing me that such was the case, I sent him all the specimens of the mineral 1 
possessed, so as to enable him to make a complete analysis of it. 
I shall not now enter into its chemical composition, merely remarking that, 
as I before observed, it is evidently a potash mica, containing about twenty 
per cent. of vanadium, instead of chromium, as I had before stated. I ex- 
pect Dr. Ghent will shortly publish his analysis of the mineralin the American 
Journal of Sciences. 
The occurrence of a mineral containing so large a percentage of vanadium 
is interesting, -as, up to the present time, vanadium has been found in but 
very few substances; itis, in fact, one of the rarest of the elements, and 
although it has lately been discovered in some voleanic rocks, yet it is present 
in such small quantities—not more than one part in ten thousand—that even 
its detection is difficult .* 
The only chemist who has successfully investigated the properties of van- 
adium, is Professor Roscoe, of Manchester, and I propose to name the min- 
eral, Roscoelite, as the most appropriate name I can give it. 
AsI stated ona former occasion, the mineral occurs, associated with 
quartz, in a vein in porphyritic rock, at Granite Creek, in Eldorado Co., in 
the lower hills of the Sierra. It has been extremely rich in gold, the mica 
carrying most of the gold. The substance is interesting. under a mineral- 
ogical point of view, as affording a unique instance of so large a proportion 
of a pentavalent element entering into the composition of a mica, and offers, 
perhaps, the most curious instance of the anomalies that present themselves 
in the chemical composition of this class of minerals. 
*T think it probable that vanadium may occur in larger quantities in these rocks than 
is supposed, as I believe the methods employed for separating it are imperfect. I have 
mixed vanadium with basalt, and after treating it in the manner indicated for separat- 
ing the substance, I obtained but about 65 per cent. of the quantity added. I have 
reason to believe that it forms compounds with the alumina, iron, and silica of the 
rocks which have not been at all investigated. Since the above was written, I find that 
Dr. Hall has found vanadium widely diffused in many rocks, generally associated with 
phosphorous, although I have been unable to detect the presence of phosphorous in 
the mica. 
