348 , TRANSACTIONS OF THE 



IDOCRASE. 

 Siegel Lode, El Dorado County. ( ? ) 



IODIDE OF MERCURY. 

 Santa Barlara County. (?) 



ILMENITE. 



El Dorado County, near Georgetown, from the gold -washings; a very 

 fine cr^-stal, about an inch in diameter, with brilliant plaues. 



IRON ORES. 



(See Magnetite and Hematite.) 



IRIDOSMINE. 



With platinum and gold in the beach sands of the northern counties. 

 An analysis by C. A. Kurlbaum, Jr., in Dr. Genth's laboratory, of a sample 

 of the residue from gold washing and amalgamation obtained by the 

 author in eighteen hundred and fitty-four, gave 48.77 per cent of iridos- 

 mine. Found also as a residue in melting large lots of placer dust. 



IRON PYRITES. 



Found in most of the gold bearing quartz veins, either crystalline or 

 massive; usually from one to five per cent of the whole weight of the 

 ore. The value for gold varies greatly. At Grass Valley the concen- 

 trated sulphurets are worth from one hundred dollars to three hundred 

 dollars per ton. Cabinet specimens of this mineral may be had in very 

 large crystals, cubes, at the Fairmount claim, three miles from Pilot Hill, 

 El Dorado County. It is there associated with garnets, brown spar, and 

 specular iron. Found in brilliant druses lining fissures in the rocks of 

 the E Pluribus Unura tunnel, three miles from Murphy's, Calaveras 

 County. In brilliant, but small cubical crystals, in the gold ore of the 

 Mameluke claim, near Georgetown, El Dorado County. Mariposa County, 

 in large and perfect crystals, in the slates near the Deville Mine, south of 

 Princeton Hill. Placer County, in large crystals, near the Grizzly Bear 

 House, between Auburn and Forest Hill. 



JASPER. 



Yery fine masses of brown and yellow jasper are abundant near Mur- 

 phy's, Calaveras County, in the quartz veins, and in the debris from them. 



KERARGYRITE. 



(See CnLORiDE or Silver.) 



LIGNITE. 



San Francisco County, Contra Costa County, Monterey County ; in Amador 

 County \n thick beds, at the base of the Sierra Nevada; used in lone 



