MINERALS. 
303 
auriferous quartz of Grass Valley, and other localities. A few specimens in my collection 
contain small, brilliant grains resembling tetradymite, but tbeir exact character is not yet 
determined. 1 
AESENIC. 
This metal occurs, in connexion with argentiferous galena and sulpburets of iron and copper, 
at the Alisal Eancbo, in Monterey county, twenty-five miles from the Mission of San Carlos. 
This mineral, on being heated, passes off in vapor, and burns quickly, forming a white cloud of 
arsenious acid—the “ arsenic ” of the shops. It will thus he seen that the roasting or smelting 
of this ore would he highly dangerous to the workmen. Arsenic is a common associate of 
silver ores. 
CHROMIC IRON. 
Extensive beds of massive chromic iron are said to exist in the mountains of Monterey county. 
Masses of the ore which were submitted to me for examination proved to be fully equal to the 
best ore of the northern counties of Maryland and of Lancaster county, Pennsylvania. The 
resemblance of the specimens to the massive ore from “ Wood’s Pit ” is so close that specimens 
could not be distinguished if mingled. Crusts of emerald nickel, of the same beautiful dark- 
green color as that found on the Maryland ores, covered portions of the specimens. 
This mineral is used for the manufacture of bichromate of potash, and has been mined to a 
considerable in Maryland, and exported. A supply is now more cheaply obtained from Asia 
Minor. 
EMERALD NICKEL. 
The green coats and compact crusts which are found in the seams of the chromic iron of 
Monterey county correspond with the emerald nickel associated with the chrome ores of “ Wood’s 
Pit,” near the line between Maryland and Pennsylvania. This mineral was first brought to 
notice by Professor B. Silliman, jr., and is a hydrated carbonate of nickel, with the following 
composition in 100 parts : 2 
Oxyde of nickel_ 58. 811 
Carbonic acid_ 11. 691 
Water... 29.498 
This mineral does not occur in quantities sufficient to warrant working the locality for nickel. 
It is, apparently, a product of decomposition of the gangue of the chrome ore, for at Wood’s 
Pit a considerable amount of nickel is found in the associate minerals. 
ILMENITE. 
A beautiful compound crystal of this mineral was obtained from Georgetown, El Dorado 
county, it having been taken from the gold washings of that vicinity. The crystalline planes 
are very perfect and brilliant, but there are few modifications. The only planes noted are those 
of the rhombohedron and a broad triangular plane upon the axis, resulting from the truncation 
of the solid vertical angle. 
1 A notice of the occurrence of telluret of silver in California was communicated to the Academy of Natural Sciences of 
California, and is published in the American Journal of Science, vol. xxiii, page 270. 
! B. Silliman, jr., American Journal of Scienee, second series, vi, 248. Also in Dana’s System of Mineralogy. 
