1978 



LiMESTONK IN THK CO AS I RANGES 



41 



Table 8. Bulk analyses of limestone from the Permanente deposit, Santo Clara County (Bailey and Everhort, 1964, table 6). 



/ 2 } 4 5 6 7 8 9 10 



SiOj 29.2}% 18.4% 17.5% 16.7% 15.9% 



AljOa 1.26 1.5 1.4 1.5 1.5 



FejOj 0.54 0.7 0.7 0.7 0.7 



CaO J8.M 43.3 43.8 44.4 44.9 



MgO 0.24 0.3 0.4 0.3 0.4 



Loss on ignition .... 3066 34.3 34.7 35.1 35.7 



Total 99^ 98.5 98.5 98.7 99.1 



aCOj 68T 773 783 79l 802 



I. 9, and 10 from Logan, 1947, p. 315 



2S obtained from Permanente Cement Co. bv E, H. Bailev and D. L Everhart 



Normally the low-grade limestone, which is in- 

 terbedded with the higher grades, would be wasted. 

 However, by means of differential grinding and froth 

 flotation, the low-grade rock is sufficiently up-graded 

 to be blended into the raw feed for cement. 



Quarry operations at the Permanente deposit are 

 conducted by benching, at 50-foot intervals, in one 

 large pit near the center of the deposit. An older aban- 

 doned quarry is located in S\V'/j SE'/j sec. 18 at the 

 west end of the deposit. In 1962, the main quarry 

 covered an area about 1,800 feet bv 1,.500 feet. There 



was about 500 feet of relief between the highest face 

 and the quarry floor, the latter being at an elevation 

 of 1,350 feet. Quarry control is provided by explora- 

 tory (rotary) drilling on 100-foot or 100-foot by 200- 

 foot centers. Deep diamond drilling also is used for 

 long-range planning. 



Normal open-pit operations prevail, with selective 

 quarrying employed to maintain the proper grades of 

 limestone. Blast holes are made w ith air-circulated ro- 

 tary drills. Ammonium nitrate and oil constitute the 

 explosive. Some secondary blasting is necessary. Elec- 

 tric-powered shovels load 45-ton-capacity dump 

 trucks, which haul to primary crushers at the edge of 

 the quarry floor. The material is then crushed and 

 transferred to secondary crushers near the plant via a 

 4200-foot belt conveyor. After secondary crushing, the 

 limestone is conveyed to separate stockpiles to await 

 further processing. Weathered greenstone, obtained 

 west of the quarry and used to supply the needed 

 alumina and iron in cement, also is stockpiled here. 

 Formerly, the alumina-iron oxide fraction v\ as sup- 

 plied by purchasing laterite produced in Amador 

 ("oiintv. 



Pholo 6. View to west of large multi-benched quorry at Permanente lime- 

 stone deposit, 1969. The quarry is developed in chert-bearing limestone 

 (Fronciscon Formation), which is the principal row material used at the 

 nearby cement plont. Photo courtesy of Kaiser Cement and Cypwm Corp. 



Photo 7. Aerial view of Kaiser Cement ond Gypsum Corporotion's cement 

 plant at Permanente in 1969. The plant, which is the lorgest in the west, has 

 six kilns and on onnual copocity of 8,500,000 barrels of cement. Photo 

 courtesy of Kaiser Cement and Gypsum Corp. 



