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Santa Cruz County History - Making a Living
Mineral Survey of Santa Cruz County - Limestone
by C. McK. Laizure
Prepared by C. McK. Laizure,
Mining Engineer of the California State Mining Bureau
This property, formerly known as the Thurber Quarry, contains 23 acres, situated two miles northwest of Santa Cruz, adjacent to holdings of the Pacific Limestone Products Company. The rock varies from a coarsely-crystalline white or bluish-white limestone to a finer-grained hard siliceous limerock. There is a small crushing plant containing a 9x14-inch Blake crusher for preparing the stone for macadam and concrete work, the only purposes for which it is used. The quarry has been worked up to the property line on one side and, as there is increasing overburden on the present face, the owner is considering starting a lower bench near water level. The quarry is worked in a small way only, an average of two men being employed the year round. Owner, W.E. Miller, 81 Church street, Santa Cruz.
Pacific Limestone Products Company
Home office, plant and quarry at Santa Cruz; sales office, Postal Telegraph Building, San Francisco. Officers: F. W. Johnson, president; D. L. Martin, vice-president; W. C. Johnson, secretary.
This company was organized in 1923 and took over the old Caplatzi Quarry which had been operated on a small scale by former owners for many years. Since the property was taken over by the Pacific Limestone Products Company, the number of raw limestone products prepared for specific purposes has been greatly increased and they are now being used for terrazo, stucco dash, chicken grit, roofing grit, commercial fillers, glass manufacture, motor sand, concrete brick, cattle lime, poultry lime, fertilizer, macadam, and other uses. By the installation of additional equipment at the plant and sales promotion work carried on among prospective users of raw limestone products, the company has succeeded in quadrupling the output of the quarry in the past two years.
The property comprises 14 ½ acres located at the end of Spring street, Santa Cruz, two miles northwest of the Southern Pacific depot, at an elevation of 250 feet. The deposit is a limestone rock, medium hard with very fine to very coarse crystals. The rock is shattered and broken in large masses and is bluish-white in color. The average face is 52 feet high with an overburden of from 2 to 8 feet of soil and red clay. The overburden is removed by shooting with black powder to the floor of the quarry, or else it is trapped in a 10-yard bin chute. If the overburden is shot to the quarry floor, it is picked up by a Haiss loader and loaded into wagons or trucks. A good deal of this overburden is sold for fill material. All that is not sold is hauled to a waste dump.
Rock is blasted down with 10 to 14-foot toe holes averaging 8 to 10 feet from the face with 40 per cent L. F. Extra Giant 7/8 x 8 dynamite. Due to the many vertical seams a large amount of the rock is broken down without drilling. Air from a 6x7-inch single-stage Sullivan compressor furnishes power for a Sullivan 'Junior' rotary jack hammer. Pieces over 24 inches are plug shot. All rock is broken with 16-pound rock hammers to sizes less than 6 inches.
Because of mixed impurities of magnesium and silica all rock is hand-picked for its color, crystals and impurities. The piles of 6-inch rock are hauled to a No. 4 Austin gyratory crusher in 1 ½-yard one-horse dump carts or in one-ton Ford trucks. This crusher is about 500 feet from the present quarry face. Three men are used to fill the carts, and there is a driver for every two carts. While the driver is hauling one cart to the crusher, the other cart is being filled.
The Austin crusher reduces the stone to 2 ½ inches or smaller. This stone is then elevated by a bucket conveyor a distance of 50 feet to three gravity screens. The bucket elevator has 9x12-inch buckets spaced 12-inch centers. The screens separate out ¼, 1/8, and from 1/8 to 30 mesh sizes. The dust, if limestone is being crushed, drops into a bin directly below the screens and is sold as fertilizer. The 1/4 and 1/8-inch sizes drop to bins below the screens and in front of a No. 2 Williams hammer mill, or if desired, directly into another elevator that carries them to the grit screens.
Stone larger than ¼-inch goes to a storage bin. Stone is drawn from this storage bin and conveyed horizontally 20 feet to a 30-inch by 14-foot revolving screen. This screen has its cloth in four sections, and separations are made as the trade demands. Flux stone is made in two sizes from ½ to 1 ½ inches and from 1 ½ to 2 ½ inches. The oversize from this screen drops to a No. 2 Eureka jaw crusher. The discharge from this crusher is elevated 15 feet to a 30-inch by 6-foot revolving screen. This screen removes the dust and smaller sized crushed rock for special demands.
The discharge from the Williams mill is elevated 45 feet to a double cloth 30-inch by 10-foot revolving screen. This screen separates out four sizes. The tailings fall through a chute to a storage bin for recrushing. Each size is separated out from the screen and drops to separate storage bins. The separation from the outer screen drops to a No. 9 Rotex screen. The oversize from the Rotex screen passes to a storage bin directly over a No. 2 Williams pulverizing mill which grinds the material to fertilizer limestone. The discharge from this Williams mill is elevated 35 feet and passes
[A section of text is missing from the original publication at this point.] special products can be produced without any difficulty.
The plant operates the entire year. Sixteen men constitute the average working force. Four men are employed in the mill and sacking department, four men handle all hauling, and the rest are used in the quarry. During rush periods the force has been increased to 36 men.
State Mineralogist's Report XII, p. 395;
XIII, p. 631; XVII, p. 237.
Pit and Quarry, Vol. 10, No. 5, June 1, 1925, pp.55-58.
|Bituminous Rock||Gold||Mineral Water|
|Black Sand||Granite||Moulding Sand & Peat|
|Cement||Iron||Petroleum & Potash|
The Mineral Survey of Santa Cruz County was printed in the Santa Cruz Chamber of Commerce Annual Report, 1926. Reproduced by permission of the Santa Cruz Area Chamber of Commerce.
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