1978 



Limestone in the Coast Ranges 



65 



The main limestone deposits are centered on "hill 

 1981" about a mile north of the dolomite deposits. 

 Perhaps the largest limestone deposit covers an east- 

 trending area about 600 feet long by 300 feet wide on 

 "hill 1981." Part of this deposit is well exposed, con- 

 sisting of blue- gray, medium- to coar.se-crystalline 

 limestone. According to Oliver E. Bowen (1968, per- 

 sonal communication), lenticular replacement 

 patches of dolomite a few inches thick and several feet 

 long are present but do not appear to make up a sub- 

 stantial volume of the mass. Patches and laceworks of 

 siliceous material indicate a probable silica content of 

 2 to 5%. 



Many smaller lenses arc present in the vicinity of 

 "hill 1981" and southwest of there (plate 2). Some of 

 these consist of relatively pure limestone and others 

 contain substantial amounts of dolomite and siliceous 

 impurities. Because of the apparent small sizes of these 

 limestone bodies and the abundance of quartz-mica 

 schist interbeds and granitic dikes, only three or four 

 of the larger bodies seem worthy of prospecting. Max- 

 imum reserves of economically recoverable limestone 

 probably do not exceed 1 or 2 million tons. None of 

 the Martin Ranch deposits had been explored by drill- 

 ing as of June 1969 (Thomas H. Rogers, 1969, personal 

 communication). 



Other reference: Toliaferro, 1943, mop. 



McCray Ranch deposits. Location.: E'/^ sec. 4, T. 

 14 S., R. ^ E., M. D., V/i miles south of Hollister; 

 Gonzales l.>-minute quadrangle. Ownership: Dr. Rol- 

 lin Reeves, Salinas (1964). 



A nearly continuous succession of detached masses 

 of dolomite extend for half a mile in a northeast-trend- 

 ing zone in SE'/, sec. 4. Actually, these masses may be 

 remnants of a single pendant connected with the Kai- 

 ser-Harris deposit to the northeast which is now cut 

 in numerous places by granitic rock. 



Several salients of dolomite and a small zone of lime- 

 stone extend to the southwest into the McCray Ranch 

 from the Kaiser-Harris pendant and, with one excep- 

 tion, none appears to be of sufficient size to be eco- 

 nomic. One salient of dolomite extends to the south 

 where it connects with a mass of dolomite that extends 

 about half a mile southwest to the edge of the Reeves 

 Ranch. The dolomite mass appears to be cut by nu- 

 merous granitic dikes so that it may actually consist of 

 a number of small disconnected masses of dolomite. 

 Much of the dolomite is white and of good quality. 

 During the early 1960s, the deposit was drilled and 

 acquired by Inorganic Chemicals Division of EMC 

 Corporation. Reserves of dolomite may be fairly large, 

 although considerable granitic material is probably 

 present. 



No chemical analyses of the dolomite are available. 

 However, two samples of limestone collected at the 

 ridgecrest near E'/< cor. sec. 4 were shown to be of high 

 grade, based on chemical analyses by Abbot A. Hanks, 

 Inc. (Bowen and Gray, 19.';9, p. 36). The limestone is 



medium to coarse crystalline, light gray to blue gray, 

 banded, and platy. The limestone mass is probably too 

 small to be of significant commercial value. 



McPhail deposit. Location: SE'/ sec. 13, T. 14 S., 

 R. 5 E. and SW/, sec. 18, T. 14 S., R. 6 E., M.D., 10 

 miles south-southeast of Hollister; Gonzales 15- 

 minute i]uadrangle. Ownership: Amy McPhail of 

 Hollister and others. 



An undeveloped deposit of crystalline carbonate 

 rocks of the Sur Series is shown by R. E. Dempster 

 (unpublished mapping shown in Jennings and 

 Strand, 19.58) as occupying the summit of a 2,240-foot 

 hill. The deposit is shown to trend northwest and to 

 cover an irregular area of half a mile by a quarter of 

 a mile. From a distance, the deposit appears to consist 

 of several detached masses of carbonate rock as in- 

 dicated by sporadic outcrops. Close examination is 

 needed to determine the nature of the deposit and the 

 advisability of additional prospecting. Dirt roads lead 

 from Cienega \'alley, via Indian Canyon or Thomp- 

 son Creek, to within half a mile of the deposit on the 

 west and south. The deposit is referred to in the litera- 

 ture as the McPhail or Archer Lime Company deposit 

 of sec. 13 but has never been described in detail. 



References: Bradley ond Logan, 1919, p. 640; Laizure, 926, p. 237; Averill, 

 1947, p. 52; Logan, 1947, p. 276; Bowen and Gray, 1959, p. 38. 



Melendy Ranch (Willow Creek) deposit. Loca- 

 tion: S'/, sec. 21, NE'/^ sec. 28 and VV'/, sec. 27, T. 15 S., 

 R. 7 E., M.D., 20 miles southeast of Hollister; San 

 Benito 15-minute quadrangle. Ownership: George 

 Melendy Ranch and others (1947). 



Crystalline limestone of the Sur Series lies along the 

 San Andreas fault zone as a series of broken masses 

 and slivers which constitute the Melendy Ranch 

 deposit. These masses cover an area I'X miles long by 

 a maximum of 500 feet wide and extend southeast of 

 the highway bridge in sec. 21. Most of the limestone 

 is blue gray to white, somewhat siliceous, and strongly 

 brecciated — the breccia fragments ranging in length 

 from a few inches to 50 feet or more. The breccia is 

 partly cement with calcite, but many of the fractures 

 are filled with "mountain leather" (matted, fibrous 

 asbestos) and other impurities. Noncarbonate meta- 

 morphic and sedimentary rocks are intermixed to 

 varying degrees with the limestone blocks and masses, 

 rendering most of the deposit impure. A composite 

 sample of limestone collected across a width of 75 feet 

 near the south end of the deposit by Logan ( 1947, p. 

 275) and analvzed bv .Abbott \. Hanks, Inc., showed 

 92.08% CaC()„ 2.99% MgCO,. and 4.59% SiO,. 



Although total reserves are probably fairly large, 

 most of the limestone is too intermingled with other 

 rocks to be extracted without extensive selective min- 

 ing and beneficiation. Relatively pure limestone ap- 

 pears to be available onlv in blocks and small masses. 

 There had been no work done on the property as of 



