ORES AND MINERALS ASSOCIATED WITH THE GOLD. 365 
The Geological Survey having, however, done little work in the platiniferous 
region, the writer has no original information of special value to offer on this 
subject. It is certain that the metals in question occur in the northern part 
of the State in considerable abundance, and it is not positively known that 
they have been found at all in the central ana southern counties. The 
practically important ores of this group occurring in northern California are 
two: native platinum, which is an alloy of this metal with iridium, rhodium, 
palladium, etc.; and iridosmine, a mixture of the two metals, iridium «and 
osmium, in varying proportions. Besides these, there are laurite, a sul- 
phuret of osmium and ruthenium; and, according to Dr. Genth, probably 
platin-iridium, a combination of platinum and iridium in different proportions. 
Laurite (named in honor of Mrs. Laura Joy) was first discovered by Wéohler 
in the platinum washings of Borneo, and afterwards found by him, in con- 
nection with platinum, gold, chromic iron, zircon, quartz, and microscopic 
diamonds, in washings from the coast of Oregon; and the same mineral, in 
all probability, exists in northern California. 
Native platinum and iridosmine occur together in the beach-sands from 
Cape Blanco to Cape Mendocino, as also at Cherokee Flat in Butte County. 
Of the quantity of these two mineral species obtained, or of their relative 
amount, no definite statement can be given.* According to Professor Pettee, 
the occurrence of platinum in the sands in the vicinity of Oroville, has 
attracted the attention of Mr. Edison, who last year was engaged in erecting 
works at that place for saving this valuable material. 
The following analyses (by Sainte Claire Deville and H. Debray) seem to 
be the only complete analyses ever made of the California platinum.t 
* The following information in reference to California iridosmine was communicated to Dr. Gibbs by the 
officers of the United States Assay Office, at New York : ‘ For the first year or two after the establishment of the 
United States Assay Office, the proportion of osmiridium in the California gold did not exceed half an ounce 
to the million of dollars. Afterward, the proportion increased till the average was seven or eight ounces to 
the million of gold. Then for a year or more the quantity diminished, but for the last year it has been as 
large as ever. These differences depend on the variable composition of the native gold and the constant dis- 
covery of new diggings. The grains of osmiridium, suitable for pens, are roundish and solid, not liable to 
exfoliate when struck or heated. They seem to have a different composition from the compressed and tabular 
crystals. The proportion of them is usually more than a tenth of all the alloy, but it is sometimes as large 
as one fifth. The carefully selected grains used by the gold-pen makers are so minute that from 10,000 to 
15,000 of them are contained in a single ounce. The very best are worth at least $250 an ounce, and a cubie 
inch, which would be equal to about eleven ounces, is worth $2,750. Am. Jour. Sci. (2) XXXI. p. 63. 
+ Ann. de Chimie et de Physique (3) LVI. p. 449. 
