Page 380 - miningincalif1927

LOS ANGELES FIELD DIVISION. 321

are 30 feet thick, then 10 feet of sand overlies the clay. A tunnel has
been driven south 300 feet to the clay shale. The clay is being mined for
the manufacture of brick and tile. The material from the different
quarries is hauled by trucks to a grinding plant having a capacity of
25 tons per day. The material first passes over a grizzly, then to roll

type of crusher. From crusher it goes to direct rotary dryer and
then to a Gruendler mill. The ground product from this mill is con-
veyed to cyclones and bag house. The products produced are high
temperature insulation materials!, concrete admixture (for use in
cement to increase the flowability of cement, 3 pounds of diatomaceous
earth to 100 pounds of cement). The clay which is mined from the

tunnel is hauled by truck to a brick and tile plant that consists of tile
and brick machines and two round kilns. Capacity of plant is 150,000
tile per month and 150,000 insulation brick per month. Natural gas
is used for fuel. Thirty-five men are employed.

Quarries and plant of The Featherstone Insulation Company, Covina, California.

Polos Verdes Ranch Deposits. Several exposures of diatomaceous
earth occur on the east slope of the San Pedro Hills, on the Palos
Verdes Ranch.

Santa Catalina Island Deposits. Diatomaceous earth occurs on Santa
Catalina. The beds are said to be 75 feet thick. Other deposits occur
in the Santa Monica Mountains, the most extensive exposure being near
Point Durma, northwest of Santa Monica.

Bibl : State Mineralogist's Reports XII, p. 406 ; XIII, p. 643 ; Bull.

38, p. 363.

DOLOMITE.

Deposits of dolomite occur on the west slope of the San Gabriel Moun-

tains, in Sees. 13, 17, T. 3 N, R. 15 W. and in Sees. 7 and 18, T. 3 N.,
R. 14 W., S. B. B. and M., between Pacoima Canyon and Grapevine

Canyon, north of San Fernando.