Aug. 17, 1877.] iis [Genth. 
CONTRIBUTIONS FROM THE LABORATORY OF THE UNIVERSITY OF 
PENNSYLVANIA. 
No. XI. 
On some Tellurium and Vanadium Minerals. 
By F. A., GENTH. 
(Read before the American Philosophical Society, August 17th, 1877.) 
Since the publication of my papers: ‘‘On American Tellurium and Bis- 
muth Minerals,’’ read before the American Philosophical Society, August 
21, 1874, and ‘“‘On Some American Vanadium Minerals,’’ published in 
the American Journal of Science and Arts, July, 1876, I have made several 
observations which I believe to be worthy of being placed upon record. 
1. NatTIvE TELLURIUM. 
Its occurrence at the Red Cloud Mine, where it is a comparatively rare 
mineral, has previously been nientioned. Recent developments in Colo- 
rado have furnished a number of new localities, in some of which it is 
found in considerable quantities and in peculiar varieties, associated 
with other very interesting minerals. 
1. In Magnolia District, Boulder County, at the Keystone Mine and 
Mountain Lion Mine (which are working the same vein), also at the 
Dun Raven Mine; it occurs in crystals and crystalline masses. The crys- 
tals are usually small and very indistinct, much distorted, cavernous, and 
the prismatic planes longitudinally, deeply striated; often surrounding 
quartz crystals ; occasionally, besides the planes of the hexagonal prism, 
rhombohedral and basal planes can be observed ; it is also found in colum- 
nar masses and, disseminated in grains, through other minerals. 
Sometimes it forms sheets and thin plates between the ores, which con- 
sist of quartz, mixed with a peculiar greenish vanadiferous mineral (? ros- 
- coelite), coloradoite, calaverite, pyrite, &c. This variety has often the 
appearance of ‘‘slickensides,’’ and is sometimes in masses as thin as paper, 
occasionally, however of an inch in thickness; it is dark grey, on a fresh 
fracture greyish white ; it is finely granular and of very little lustre. The 
specific gravity of the pure mineral (making allowance for the admixed 
quartz) was found to be 6.275. 
The analysis gave, after deducting 8.90% of quartz, as follows : 
Au — 0.60 
Te = 96.91 
Wi02 = 0.49 
FeO = 0.78 
Hg, Al,O,, MgO i 
K,0, &e. \ —— 1.15 
100.00 
PROC. AMER. PHILOS, SOC. xvir. 100. 0 
