Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean: Vol. 5, Pt. 2

MINERALS.
auriferous quartz of Grass Valley, and other localities. A few specimens in my collection
contain small, brilliant grains resembling tetradymite, but their exact character is not yet
determined.'
ARSENIC.
This metal occurs, in connexion with argentiferous galena and sulphurets of iron and copper,
at the Alisal Rancho, 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 be seen that the roasting or smelting
of this ore would be 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 darkgreen 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 hrome 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 Science, second series, vi, 248. Also in Dana's System of Mineralogy.
303