86 



California Division of Mines and Geology 



Bull 197 



lished thesis) , who considers the exposures to be possi- 

 bly "continuous or nearly so" with the main body. 

 The exposures were not examined by this writer. 



Two thin, subparallel bodies of limestone, probably 

 separated by a fault, lie northeast of the main body. 

 Bedding attitudes could not be measured, but overall 

 distribution of limestone suggests the bodies are thin 

 and dip moderately to gently toward the southwest. 

 Reserves are difficult to estimate without drill data 

 but probably are relatively small. 



Development of the Dubost deposit has been lim- 

 ited to minor production of limestone (for lime), al- 

 though there were two episodes of exploratory 

 drilling. In 1946, H. W. Gould and Company held a 

 lease on the property and did extensive core drilling, 

 part of which was conducted north of the main depos- 

 it on the lower of two terraces (Logan, 1947, p. 303). 

 Fourteen holes totaling 1,742 feet were drilled and an 

 average analysis of 91.32% CaO and 5.17% SiOz was 

 computed for the samples obtained. The few samples 

 analyzed for magnesia contained less than 0.25% 

 MgO. The company estimated (preliminary) lime- 

 stone reserves at more than 50 million tons although 

 only 1 to 2 million tons were proved by drilling (Lo- 

 gan, 1947, p. 304). From 1955 to late 1962, Collier 

 Carbon and Chemical Corporation leased the deposit 

 and did additional diamond drilling, including both 

 vertical and diagonal holes in the main body. Results 

 of that program are not available. 



Future potential of the Dubost deposit is somewhat 

 uncertain because of the size, location, and quality of 

 the limestone. Based on quality alone, the limestone 

 undoubtedly would be satisfactory for cement and 

 certain other purposes but not for lime, chemical, and 

 other uses where high chemical quality is important. 

 Reserves of this deposit may be insufficient to estab- 

 lish a cement plant. 



Huasna area. Location: NW'X T. 32 S., R. 16 E. 

 and E/j T. 32 S., R. 15 E., M.D., 13 to 18 miles east of 

 Arroyo Grande; Nipomo 15-minute quadrangle. 

 Ownership: Not determined. 



According to Aubury (1906, p. 80), "an extensive 

 deposit of buff colored limestone" is situated on the 

 properties of Dawson, Lowe, and Mrs. R. Porter, as 

 well as on U.S. Forest Service land. The area referred 

 to is underlain extensively by the Monterey Forma- 

 tion, which commonly contains calcareous (forami- 

 niferal) mudstone and siltstone beds, as well as 

 impure dolomite. However, there are no deposits of 

 limestone known to be of economic interest in the 

 Huasna area. A description and geologic map of the 

 rock units of this area are given by Hall and Corbat6 

 (1967). 



Kesseler (Kessler) deposit. Location: Sees. 9 and 

 16, T. 31 S., R. 15 E., M.D., 14 miles northea.st of 

 Arroyo Grande; Nipomo 15-minute quadrangle. 

 Ownership: Not determined. 



Irregular masses of onyx marble and related carbon- 

 ate material are exposed intermittently over a length 

 of half a mile in the vicinity of Salt Creek. The masses 

 are found in sandstone and shale, apparently as frac- 

 ture fillings related to the East Huasna fault. The 

 following description of the deposit is based largely on 

 reports by Angel (1890, p. 584-585) and Aubury 

 (1906, p. 111-112). At the main quarry to the east 

 (south?), the onyx occurs as steeply dipping layers 1 

 to 10 inches thick and varies from white to yellow, 

 green, and red. Half a mile to the west (north?), the 

 stone is white, faintly banded, and occurs in two lay- 

 ers 1 to 6 inches thick. Other small masses of carbonate 

 rock are found on the hill between the above expo- 

 sures. A chemical analysis of the onyx shows 93.86% 

 CaCO,, 1.43% MgCO,, and 3.93% FeCO, (Waring, 

 1915, p. 165). Several saline springs and seeps are ac- 

 tive in the vicinity and probably are related to the 

 formation of the onyx. 



The Kesseler deposit was worked from about 1890 

 to 1900 through two quarries half a mile apart. The 

 main (east) quarry was developed over a length of 50 

 feet and a height of 20 feet, exposing onyx marble 15 

 feet thick. Because the marble took a good polish and 

 could be obtained in large slabs, it was shipped widely 

 for ornamental uses. Total production is reported to 

 have been more than 1,000 tons prior to 1900. Later 

 attempts to develop the deposit were unsuccessful. 

 However, the deposit has been utilized informally as 

 a mineral collecting site, and much onyx marble has 

 been taken for lapidary purposes in recent years. 



Other references: Laizure, 1925, p. 527; Franke, 1935, p. 432. 



Lime Mountain deposit. Location: Sees. 1 5 and 

 16, T. 26 S., R. 9 E., 18 miles west of Paso Robles; 

 Adelaida and San Simeon 15-minute quadrangles. 

 Ownership: Eaton and Smith, 1215 Michigan Street, 

 San Francisco (1963). 



The Lime Mountain limestone deposit has been un- 

 der development since 1932, and production has been 

 substantial. According to Logan (1947, p. 304-305) 

 and unpublished data, commercial production was in- 

 termittent between 1933 and 1943 by Charles Taylor 

 and in 1945 by San Miguel Lime and Development Co. 

 Based on the sizes of the quarries reported by Logan, 

 total amount of limestone quarried prior to 1946 prob- 

 ably was about 200,000 tons, well over half of which 

 must have been sold. Records indicate that subsequent 

 production in 1947 and in 1949 was by Essential In- 

 dustries, Inc., and between 1952 and 1953 by Henry C. 

 Dalessi, the latter operating the property for the Cen- 

 tral Bank of Oakland. The present owner acquired the 

 deposit in late 1953 and has operated it on a seasonal 

 basis ever since. Total limestone produced (sold) 

 through 1963 is estimated to be more than a million 

 tons. All of the limestone quarried was obtained from 

 the summit area of the main limestone body in NW'X 

 sec. 15 and virtually all of the production was for use 

 in beet-sugar refining. 



