1978 



Limestone in the Coast Ranges 



81 



Larger masses of impurities, which are not too com- 

 mon, generally can be avoided by selective mining. It" 

 the limestone is used for cement, a high silica content 

 actually may be desirable. Other contaminating 

 materials associated with the limestone are schist and 



Table 17. Chemical anolyses of carbonate rock samples from 

 Pico Blanco deposit (see figure 6 for locations). 



Sjmp/e SiOs 



PB-1 :..>6% 



PB-2 0.69 



PB-3 3.90 



PB-4 0.17 



PB-5 6.12 



PB-« 0.55 



PB-7 0.27 



PB-8 on 



PB-9 0.50 



PB-IO 0.47 



PB-11 0.31 



PB-I2 0.81 



PB-13 0.66 



PB-14 0.20 



PB-15 0.18 



PB-16 2.78 



PB-17 0.70 



PB-18 0.84 



PB-19 0.69 



PB-20 • 0.84 



PB-21 0.67 



PB-22 1.01 



PB-23 0.22 



PB-25 0.62 



SPB-1 0.94 



SPB-2 0.76 



SPB-J 0.32 



SPB-4 0.21 



PBy-lA 0.70 



PBy-lB 0.52 



PBv-lC 0.66 



PBy-lD 0.58 



PBy-2' 23.40 



PBy-3 0.72 



PBy-4 3.10 



PBy-5 0.88 



PBy-6 1.18 



PBy-7 1.92 



PBy-8 1.48 



PBy-9 0.72 



PBy-IO 2.16 



PBy-11 7.32 



PBV-12A 3.92 



PBvl2B' 1.12 



PBy-13* 17.94 



PBy-14 0.70 



PBy-15 0.44 



PBv-16 1.74 



FesOs A/^3 CM MgO P^U, 



0.08% 



0.04 



0.12 



0.02 



0.10 



0.13 



0.02 



0.04 



0.07 



0.16 



0.08 



0.05 



0.05 



0.06 



0.05 



0.03 



0.05 



0.06 



0.05 



0.13 



0.06 



0.(H 



0.02 



0.02 



0.47 



0.08 



0.06 



0.05 



0.08 



0.05 



0.06 



0.05 



0.14 



0.07 



0.08 



0.04 



0.02 



0.03 



0.05 



0.10 



0.16 



0.19 



0.11 



0.06 



0.19 



0.08 



0.03 



0.04 



0.44% 



0.17 



0.92 



0.04 



1.27 



0.14 



0.08 



0.04 



0.12 



0.10 



0.08 



0.22 



0.21 



0.08 



0.06 



088 



0.20 



0.24 



0.18 



0.21 



0.16 



0.23 



0.07 



0.13 



0.20 



0.13 



0.07 



0.05 



0.14 



0.06 



0.14 



0.10 



0.38 



0.15 



0.16 



0.08 



0.06 



0.10 



0.18 



0.20 



0.32 



0.36 



0.23 



0.12 



0.22 



0.16 



0.11 



0.14 



53.66% 



54.92 



52..56 



55.52 



51.43 



54.54 



55.70 



55.69 



55.30 



36.88 



55.56 



54.87 



54.78 



55.58 



55.08 



53.29 



54.82 



54.89 



55.12 



42.40 



50.35 



54.59 



55.35 



55.00 



53.47 



51.14 



52.36 



55.21 



55.04 



55.09 



52.13 



53.81 



42,28 



53.96 



53.32 



55.09 



54.65 



54. .56 



54.25 



55.17 



54.01 



50.47 



52.83 



35.30 



44.83 



54.71 



54.31 



54.58 



0.46% 



0.48 



0.48 



0.26 



0.19 



0.83 



0.07 



0.14 



0.24 

 15.89 



0.14 



0.42 



0.52 



0.18 



0.59 



0.42 



0.48 



0.36 



0.23 

 10.96 



4.33 



0,49 



0,59 



0,37 



1.30 



3.66 



2,80 



0.49 



0.33 



0,43 



2,77 



1.43 



0,17 



1.19 



0.57 



0.24 



0.49 



0.41 



0.59 



0.18 



0.38 



0.71 



0.53 

 16.95 



0.58 



0.64 



1.08 



0.23 



0,04% 



0.02 



0.03 



0.04 



0.05 



0.01 



0.02 



0.01 



0.04 



0.02 



0.03 



0.01 



0.03 



0.02 



0.03 



0.01 



0.02 



0.02 



0.03 



0.03 



0.02 



0.02 



0.03 



0.05 



0.11 



0.05 



0.05 



0.05 



0.20 



0.07 



0.21 



0.20 



0.05 



0.21 



0.14 



0.04 



0.04 



0.05 



0.19 



0.20 



0.20 



0.26 



0.21 



0.01 



0.04 



0.20 



0.19 



O.OS 



• Sample analy7.ed lo determine range of SiOa or MgO or for ottier special 

 purposes. 



Samples PB-1 to PB-12 collected by Oliver E Bowcn and Earl W. Han March 

 27, 19.^7. and analyzed by Abbot A, Hanks, Inc. San Francisco. 



Samples PB-H lo PB-2? collected by Oliver E. Bowcn June 27, I9S7, and 

 analyzed by AIjIkji A. Hanks, Inc. 



Samples SBP-I to SBP-4 collected by Tom Maher (previous owner) March 

 I95H and analyzed for Division of Mines bv Abtjot A, Hanks, Inc, 



Samples PBy-1 to PBy-lA collected by Marshall E Maddock October I, 1959, 

 (outcrops painted yellow) and analyzed by Abbot A, Hanks, Inc, (per- 

 mission to publish courtesy O P Jenkins, owner). 



gneiss interbeds and granitic dikes. These rocks usu- 

 ally are restricted to the marginal parts of the lime- 

 stone bodies and may not present serious mining 

 problems. 



Through early 1961, development of the Pico Blan- 

 co deposit had been restricted to sampling and geolog- 

 ic mapping. A few test pits have been developed on the 

 claims as a part of the assessment work and, since 1961, 

 limited core drilling has been done, but drill data are 

 not available. 



Prior to 1961, samples from 44 localities (figure 6) 

 were analyzed for chemical composition (table 17). 

 Although an insufficient number of samples was 

 analyzed to delineate areas of various quality lime- 

 stone, sampling and field inspection indicate that the 

 great bulk of the Pico Blanco and Hayfield bodies 

 consists of good quality limestone that averages about 

 .''4 percent lime. It is apparent that the limestone is of 

 sufficiently high quality for cement. Moreover, analy- 

 ses suggest that some of the limestone is adequate for 

 most lime, chemical, and metallurgical uses. 



Reserves cannot be estimated accurately because ex- 

 act thicknesses of the bodies are not known. However, 

 if it is assumed that the Pico Blanco body has an aver- 

 age thickness of .SOO feet, maximum limestone reserves 

 north of the South Fork of the Little Sur River and 

 above 1,600 feet elevation are estimated to be in the 

 order of 600 million tons. Although parts of the depos- 

 it are thinner than 500 feet, a maximum thickness of 

 over 1,.500 feet is estimated by Marshall E. Maddock 

 (1960, unpublished report for Olaf P. Jenkins), and 

 the reserve estimate is probably conservative. On the 

 other hand, reserves could be reduced significantly 

 depending on the quality and uniformity of limestone 

 required for a particular use, the amount of selective 

 mining necessary, and the amount of deleterious 

 materials associated with the limestone. The max- 

 imum reserves of the Hayfield body north of the river 

 are estimated to be about 20 million tons, assuming an 

 average thickness of 100 feet. 



By any standard, the Pico Blanco body is enormous 

 and obviously of strong economic potential. The most 

 serious drawback to its development is its relatively 

 remote location, especially with reference to markets 

 or established major transportation lines. Its location 

 in an area of potentially high recreational and wilder- 

 ness value may also present some development prob- 

 lems. 'The owners are reported tt) be exploring the 

 feasibility of various alternative methods of extraction 

 and transportation that v^ould permit development 

 with minimal impact on other values. 



Other references: Trosk, 1926. p. 131, mop; Logan, 1947, p. 260. 



Sierra (Serra) Ilill-Littlc Sur deposits. S'/; T. 18 

 S.. R. 1 E., M.D., extending from the NW% sec. 19 

 southeastward to the E'/, cor. sec. 34, accessible from 

 State Highway 1 and the Old Coast Road; Point Sur 

 1.5-minute quadrangle. Ownership: Not determined 

 (1957). 



