70 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. 
[BULL. 167. 
material is a highly metamorphosed contact limestone, carrying an 
abundance of cinnamon garnet and occasionally a green pyroxene. 
Now and then there is embedded in the masses of garnet a dark-gray 
mineral, nearly black in some specimens, in brilliant plates which 
nowise suggest epidote. Epidote, however, it proved to be, as shown 
by the subjoined partial analysis, and as verified by Mr. J. S. Diller 
under the microscope. The anorthite, also determined optically by 
Mr. Diller, and analytically by Mr. George Steiger, is associated some- 
times with the epidote and sometimes in coarse crystals only with 
the garnet. The analyses are as follows : 
Si0 3 ... 
A1 2 3 ... 
Fe 2 3 .- 
FeO ... 
CaO ... 
MgO... 
Ignition 
Epidote. 
100.70 
Anorthite. 
38.54 
45.62 
28.39 
35.29 
6.89 
.50 
24.12 
17.31 
trace 
2.26 
98.22 
In some ways the epidote resembles axinite, a mineral which has 
long been recorded as found at Phippsburg. Is the supposed axinite 
really epidote f 
9. Roscoelite. 
The rare mineral roscoelite has greatly needed reexamination, in 
order to reconcile the discrepancies between the analyses of Roscoe and 
Geuth and to establish a satisfactory formula for this supposed vana- 
dium mica. To the kindness of Mr. G. W. Kimble, of Placerville, Cali- 
fornia, I am indebted, through Mr. H.W.Turner, for specimens from the 
Stockslager mine, from which a limited amount of fairly pure material 
was picked out. This was then laboriously purified by the aid of 
Thoulet's solution, the result being a very nearly pure product weigh- 
ing only 1.2 grams and having, after drying at 100° C, a density of 
2.97 at 20° C. 
Notwithstanding the small amount, it was possible by the exercise 
of care to make fairly satisfactory analyses. 
With regard to the methods employed little need be said except as 
to the determination of the condition of the vanadium. For this purpose 
decomposition was effected by rather dilute H 2 S0 4 in sealed tubes, the 
greatest care being taken to expel every trace of air from the powder 
and acid, and to seal the tube during passage of a current of 0O 2 . 
Otherwise it is impossible to prevent oxidation of a considerable part 
