52 



California Division of Mines and Geology 



Bull. i97 



the extensive Monterey Formation (?) . The mudstone 

 is obtained by the operator from a hillside quarry 

 located a mile northeast of the plant, near NW'/ cor. 

 sec. .H, and is shipped to the plant by rail. The materi- 

 al quarried is brownish gray, buff weathering, nonfis- 

 sile, brittle, siliceous, and probably tuffaceous. 

 Typical analyses of the mudstone, furnished by the 

 company in 1961, ran as follows: 73-81% SiOj, 7.5- 

 11.0% AljO,, 1.75-2.25% Fe^O,, 0.8-1.0% CaO, 0.4^ 

 0.6% MgO, 0.8-1.1% KA and 0.3-0.6% Na^O. 



Annual rated capacity of the plant is 3 million bar- 

 rels of cement. Yearly production is reported by Bow- 

 en and Gray ( 1962, plate 2, p. 4) to be roughly 840,000 

 tons of limestone and associated noncarbonate rock 

 and 85,000 tons of mudstone (shale) . Total production 

 of limestone from the San Vicente Creek deposit is 

 estimated to be about 25 million tons since 1907. 



Pacific Cement and Aggregates Division owns an- 

 other limestone deposit near Bonnie Doon. They re- 

 cently drilled this deposit to determine its potential as 

 an additional source of cement raw material (see Bon- 

 nie Doon deposit).! 



Other references: Huguenin and Costello, 1920, p. 233, 239; Laizure, 

 1926, p. 75-78; Hubbard, 1943, p. 37-39; Logon, 1947, p. 320-321; Leo, 

 1967, p. 30; Clark, 1970. 



Smith Grade deposit. Location: E'/ sec. 25, T. 10 

 S., R. 3 W., M.D., 7'/, miles northwest of Santa Cruz; 

 Felton 15-minute quadrangle. Ownership: Not deter- 

 mined (1963). 



Crystalline limestone exposures along Smith Grade 

 Road and Reggiardo Creek have been mapped as a 

 relatively large deposit by Branner et al. (1909, map). 



t Quarrying at the San \'icente Creek deposit ceased in mid-1970 concurrent 

 with the opening of the Bonnie Doon deposit 2 miles to the southeast {see 

 footnote under Bonnie Doon deposit). The San \'icente Creek deposit 

 will be held as an emergency reserve. A major reason for its closing is 

 believed to have been the cost of removing increasing amounts of over- 

 burden. 



Leo (1967, p. 31; and unpublished Stanford thesis), 

 and Clark (1970). The limestone commonly is coarse 

 crystalline and high in calcium, but locally it is im- 

 pure. Calc-silicate rocks, containing as much as 60% 

 wollastonite, are exposed along the road, 1,000 feet 

 west of the E'/ cor. sec. 25; other silicate minerals are 

 reported elsewhere in the limestone deposit. Quartz- 

 ite and schist are locally exposed around the borders 

 of the limestone and probably also exist as interbeds. 

 Granitic dikes west of the creek further reduce the 

 purity of the deposit. 



As of August 1963, there was no known develop- 

 ment. The deposit appears to be of only minor eco- 

 nomic interest because substantial reserves of good 

 quality limestone are not evident. 



Wagner's Park deposit. Location: Probably 1 mile 

 north of Santa Cruz business district; Santa Cruz ly^- 

 minute quadrangle. Ownership: Not determined. 



"Soft limestone" or "calcareous tufa" from a small 

 gulch, at a place known as Wagner's Park, and clay 

 from a nearby bluff were used experimentally by Cali- 

 fornia Portland Cement Company (not the same as 

 the firm currently operating in southern California) 

 to produce portland cement around 1877. The com- 

 bined materials were processed in a reverberatory fur- 

 nace and kiln. Some cement was produced, but little 

 or none was sold. The lack of success is reported to be 

 due to litigation (Williams, 1883, p. 464) and competi- 

 tion from imported cement (Crawford, 1894, p. 380). 



Chemical analyses (Irelan, 1888, p. 881) show two 

 samples of limestone to contain 50.31% and 50.02% 

 CaO, 2.40% and 4.71% SiO^, and 1.45% and 1.80% 

 alkalies. Irelan also presents chemical and physical 

 data for cement, as well as chemical analyses for the 

 clay and shale raw materials. 



Other references: Williams, 1885, p. 676; Aubury, 1906, p. 184; Bowen 

 and Gray, 1962, pt. 1, p. 6. 



