302 
GEOLOGY. 
pieces of galena. Mines of gold and silver are also said to have been found about fourteen 
leagues from San Diego. They were once worked by a man from Guanajuato. 1 
Silver, in combination with tellurium, has been found at two or more places in the mining 
region, in the auriferous drift. It is reported, also, that a fragment of native silver was obtained 
from the auriferous gravel near Mokelumne Hill. 
We may look with considerable confidence for argentiferous minerals in the region of the 
great belt of the metamorpbic limestone, which traverses several counties, if not the entire length 
TELLTJRET OF SILVER—HESSITE ? 
A mineral, which gives all the reactions for tellurium and silver, was obtained near George¬ 
town El Dorado county. It resembles a fragment of tarnished lead or silver glance, but is 
chiefly composed of silver and tellurium, and is probably the species Hessite. The mass is about 
one inch in length and breadth, and is entirely free from gangue, but incloses native gold, which 
appears at several points on its surface. An aggregation of cubical crystals, resembling galena, 
is implanted on one side, and the other is deeply indented with angular cavities, probably the 
print of quartz crystals. 
The massive portions of the specimens are sectile and malleable, and do not show any traces of 
crystalization ; they may be cut with a knife, like lead, and give a brilliant metallic surface. 
The hardness is about equal to 2 on the scale of Mohs. 
In the open tube, before the blowpipe flame, the mineral fuses quietly, coloring the glass a 
bright yellow under the assay ; a white, or gray, sublimate is deposited at a short distance, or 
immediately over it, which, on being heated, fuses into transparent drops resembling oil. On 
charcoal it fuses readily to a leaden-colored globule, which, on cooling, becomes covered with 
little points or dendrites. This globule flattens under the hammer, but breaks on the edges. 
With the addition of a little carbonate of soda, a globule of silver is readily obtained. A frag¬ 
ment, heated to redness in a closed tube or matrass, with carbonate of soda and charcoal dust, 
gives' on the addition of a few drops of boiling water, the beautiful violet-red or purple solution 
described by Berzelius as characteristic of tellurium. This solution loses its color after standing 
for some time, and a dark-colored powder is deposited. The mineral dissolves in hot nitric acid, 
with the separation of tellurous acid in crystals. The specific gravity is found to be 8.33. 
The color of this mineral is darker than the Hessite of Savodinsky, Siberia, and it is not quite 
so hard. Hessite, according to the analysis by G. Rose, has the following composition : 2 
Tellurium.. 36 - 96 
Silver.-. 62 ' 42 
Iron... 24 
I am indebted to P. C. Currier, esq., of Georgetown, for the specimen which has been 
described. It was obtained in that vicinity, and probably taken from the auriferous drift with 
gold, but it cannot have been transported far from its original source. 
A specimen seen in the possession of a broker in San Francisco, in 1854, greatly resembled 
the massive part of the specimen just described. The small fragment of it which was then 
obtained also gives the reactions for tellurium and silver. Its precise locality is not known. 
It is probable that tellurium, combined with silver, lead, or bismuth, will be found in t e 
1 De Mofras’ Exploration of Oregon and California. 
s Quoted in Dana’s Mineralogy, vol. ii., page 44. 
