Minerals and Mines of San Diego. 71 



In the Eisinore district we would mention the occurrence of 

 large beds of potters' clay, fire clay, fire sand, "sewer pipe clay," 

 mineral paint, yellow ochre, steatite (soap-stone), associated with 

 talc and chlorite, asbestos and coal- Large quantitie s of pottery 

 is now being made for the San Diego and Los Angeles market. 

 The asbestos is utilized in the manufacture of fire-proof boiler 

 ■covering; and the coal mines are being as rapidly developed as 

 possible, the quality continuing to improve as well as the prospect 

 of an abundant supply. 



We are indebted for specimens from this district of the principal 

 ores and mines to the generosity of Messrs. Banks, Warson, Hofif 

 and others, and to Mr. Ira J. Gray, business manager of the West 

 American Scientist, who volunteered to visit this and other 

 localities in the interests of the proposed exhibit of the mines and 

 minerals of the U. S., to be opened in May following in London, 

 England. Crystalized quartz, gypsum, silver and copper ores, 

 mineral gum, etc., are also among the products of the Eisinore 

 district. 



The Temescal tin mine, ten miles from Tem'^cula. in San Diego 

 county, though known for a long time, is yet undeveloped. I have 

 not been able to learn the result of an assay of the ore. 



At Penasquitas ledges of gold-bearing quartz have been opened, 

 and also at San Jacinto, where extensive marble quarries await 

 development as well. 



Molybdenite occurs in the granite rocks at Campo,and is found 

 associated with silver ore in the Jacumbe district, near the border 

 of the Colorado desert. The ore at that locality assays about $28 

 to the ton in silver. 



Quartz ledges in the Jamul district assay $6 to $8 in gold and 

 silver, but are undeveloped. 



Mica has not yet been found in any quantity of a paying quality. 

 A beautiful golden mica comes in flakes as large as one's hand 

 from Wilson's mine, near Warner's ranch. It occurs in small 

 quantities throughout the mountains south into Lower California, 

 where the jet black form is also found. 



The San Rafael mining district, though comprising Mexican 

 territory, deserves attention, as well as other mining regions of 

 Lower California, because they are adjacent to and depend upon 

 San Diego for supplies. At San Rafael are numerous very rich 

 quartz veins, which have and are capable of producing large quan- 

 tities of gold. Rich gold-bearing ^ulphurets are found in great 

 quantities. Coal, silver, sulphur, iron, nickel, copper, etc. , are 

 among the immense ore deposits of this portion of the district 

 which lies 95 miles southeast of San Diego. 



Still more valuable deposits are found further south of silver, 

 iron and copper; and famous placer mines have been worked in 

 the mountains of the peninsula, annually producing much gold in 

 nuggets or coaise " dust." 



