IX, A, 2 Pratt: Geology of Cement Materials 155 



an accumulation of chemically precipitated calcium carbonate 

 or, possibly, of very small, lime-secreting marine organisms. 



It would be possible to quarry these limestones advantageously 

 from either of two sites. From the bluff near the beach at 

 Tinaan, fragmental coral with the composition represented by 

 the combination of 35, 37, and 39 (Reibling and Reyes) could 

 be secured in adequate quantity. The quarry face would be 

 14 to 25 meters high, and the excavation could proceed readily 

 over an area of some 20 hectares, making available at least 

 5 million metric tons of material. The present annual consump- 

 tion of cement in the Philippines is between 300,000 and 400,000 

 barrels, while this estimated supply of limestone would permit 

 the manufacture of 500,000 barrels of cement annually for fifty 

 years. 



The alternative quarry site is in the beds of chalk, at a point 

 along the west wall of Pandan Valley about 800 meters from 

 the coast. From this site a supply of material equal to, or 

 greater than, the foregoing estimate could be obtained under 

 most economical conditions. The quarry face would be about 

 30 meters high, and there would be no overburden to remove 

 since the overlying beds do not extend so far inland (fig. 3). 



More than fifty samples have been taken from the two 

 proposed quarry sites and submitted to chemical analysis. The 

 greater number of these samples were obtained as cuttings 

 from drill holes. The test holes, which were 5 centimeters in 

 diameter and varied from 6 to 18 meters in depth, were drilled 

 with a hand drill consisting of a steel chisel-shaped bit joined 

 to a drill rod of 1-inch gas pipe. The cuttings were removed 

 from the hole by means of an earth auger (in some materials 

 a simple sand pump was necessary) attached to the drill rod 

 in place of the bit.* 



The fragmental coral beds at the quarry site nearest the coast 

 are not uniform chemically ; the average composition lies between 

 the limits shown by samples 35 and 39, and several samples 



' Hand churn drills of this type for prospecting moderately hard forma- 

 tions have been described by many writers. They are cheap, easily con- 

 structed, and surprisingly effective. Four Filipinos can operate such a drill 

 to good advantage. On the work at Naga, each crew was provided with a 

 tripod made of three 6-meter lengths of bamboo, which was set up over the 

 hole and used to support the lengths of drill rod as they were withdrawn. 

 With such a tripod the drill rod need be disconnected only at from 10- to 12- 

 meter intervals, and much time is saved which would otherwise be lost 

 in disconnecting more frequently and in handling the heavy tubes as they 

 are drawn from the hole and laid on the ground or lifted from the ground 

 to be reconnected. 



