1877.) 115 [Genth. 
4. The largest quantities of native tellurium have been observed at the 
John Jay Mine, in Central District, Boulder County, Colorado. I was 
informed that masses of 25 pounds in weight had been found there. I am 
indebted to the owner, Mr. A. J. Van Deren, for very fine specimens, 
which were taken from his mine at a depth of 30 to 35 feet. 
The tellurium is more or less mixed with quartz, it is granular to colum- 
nar in structure and of a color between tin-white and lead-grey. In the 
cavities and on the surface are rarely found tellurous oxide or tellurite, in 
minute crystals. 
A very pure specimen, after the deduction of 14.08% of quartz, con- 
tained : 
Au = 1.04 
Ag = 0.20 
Zn — 0.382 
Fe = 0.89 
Te = 97.94 
100.39 
2. HESSITE. 
My friend, Mr. August Raht, wrote me from Utah on the 20th February, 
1877, that, in testing an ore from the Kearsage Mine, Dry Canyon, Utah, 
he found it to contain large quantities of tellurium, and afterwards, in an- 
alyzing a pure piece before the blow-pipe, obtained : 
Ag — 58.790 
Au = 0.1038 
It is evidently hessite, almost free from gold, similar to that which I 
described from the Red Cloud Mine, Colorado, where it has been once 
found as a very great rarity. 
3. COLORADOITE, A NEW MINERAL. 
I have mentioned the occurrence of telluride of mercury, which I have 
called ‘‘coloradoite’’ already at the meeting of the American Philosophical 
Society of October 20th, 1876. I observed it amongst ores from the Key- 
stone Mine, Magnolia District, received for examination by the late Dr. 
W. H. Wenrich, of Denver. It also occurs at the Mountain Lion Mine; 
a specimen of ore, for which I am indebted to Commodore Stephen De- 
catur, Centennial Commissioner of Colorado, and which was found at 
the depth of 8 or 10 feet at the Smuggler Mine, Ballerat District, proved 
also to be this interesting species. 
Not crystallized, without cleavage ; massive, somewhat granular; that 
from the Smuggler inclining to an imperfectly columnar structure. 
Fracture uneven to subconchoidal. Hardness about 3 ; Sp. Gr. = 8.627— 
(pure mineral, after making allowance for the admixture of native tel- 
lurium and quartz). Lustre metallic ; color iron-black, inclining to grey, 
