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Mineral Industry, California, 1919

Excerpts from

California Mineral Production for 1919,
Bulletin No. 88

By Walter W. Bradley, California State Mining Bureau, 1920, pp. 9-14.

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Slate.

"Bibliography: Report XV. Bulletin 38.

"Slate was first produced in California in 1889. Up to and including 1910 such production was continuous, there being none between that year and 1915. Large deposits of excellent quality are known in the state, especially in El Dorado, Calaveras and Mariposa counties, but the demand has been light owing principally to competition of heater roofing materials.

"A square of roofing slate is a sufficient number of pieces of any size to cover 100 square feet of roof, with allowance generally for a three-inch lap. The size of the pieces of slate making up a square ranges from 7 x 9 inches to 16 x 24 inches, and the number of pieces in a square ranges from 85 to 686. It is worth $3.50 to 10 per square, f.o.b. quarry, depending on quality. The Ferry Building, San Francisco, is roofed with Eureka slate from El Dorado County.

Squares and value of slate from 1889-1919

(Please note: Unfortunately in the table above, I did not photocopy the bottom line of the table very well so the totals are not fully shown.)

Miscellaneous Stone.

"Bibliography: State Mineralogist Reports XII, XIII, XIV, XV. Bulletin 38.

"Miscellaneous stone is the name used throughout this report as the title for that branch of the mineral industry covering crushed rock of all kinds, paving blocks, sand and gravel, and pebbles for grinding mills. The foregoing are very closely related from the standpoint of the producer. Thus it has been found to be most satisfactory to group these items as has been done in recent reports of this Bureau. In so far as it has been possible to do so, crushed rock production has been subdivided into the various uses to which the product was put. It will be noted, however, a very large percentage of the output has been tabulated under the heading 'Unclassified.' This is necessary because of the fact that many of the producers have no way of telling to what specific use their rock was put after they have quarried and sold the same.

"In addition to amounts produced by commercial firms, both corporations and individuals, there is hardly a county in the state but (sic) uses more or less gravel and broken rock on its roads. Of much of (unreadable) this, particularly in the country districts, there is no definite record kept. Estimates have been made for some of this output, based on the mileage of roads repaired.

"For the year 1919 miscellaneous stone shows a small increase in total value from the preceding year, being $3,698,944 as compared with $3,404,157 for 1918. The outlook for the current year, 1920, is not too encouraging, due to the curtailment of highway construction because of inability to sell the State Highway bonds at their present rate of interest.

"In 1919, as has been the case for a number of years past, Los Angeles County led all others by a wide margin, with an output valued at $715,524; followed by Alameda, second, with $309,572; Sacramento, third, $276,432; Contra Costa, fourth, $275,309; and Fresno, fifth, $241,213.

Paving Blocks.

"The paving block industry has decreased materially of recent years, almost to the vanishing point, because of the increased construction of smoother pavements demanded by motor-vehicle traffic. The blocks made in Solano County were of basalt; those from Sonoma are of basalt, andesite, and some trachyte, while those from Placer, Riverside, San Bernardino, and San Diego are of granite.

"Production in 1919 amounted to only 27 M., valued at $1,350, from a single producer, each, in Riverside, San Diego and Sonoma counties.

"The amount and value of paving block production annually since 1887 has been as follows:

The amount and value of paving block production since 1887

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