Mance: Quarry Industry of Southern Indiana 185 



as to the cost of blasting with high explosives were very full and 

 helpful. 



The following letter received from Mr. H. S. Gunsolus, manager 

 of the Technical Division of the DuPont Company, will be of 

 interest in this connection to any company interested in blasting 

 out limestone for cement: 



Your letter of December SOth, in reference to the cost of explosives per 

 cubic yard for blasting limestone to be used for fertilizing material is received. 



We have not replied earlier, due to our wishing to get some information 

 together which might be of assistance to you. We are going to list below 

 a number of shots which have either been supervised or witnessed by some 

 of our own technical men and we feel sure that the figures given are ap- 

 proximately correct. You understand, of course, that the variation in cost 

 is due to local conditions, stratification, mud seams, etc., as well as the 

 size of crusher to be used, which of course will regulate the size of the broken 

 stone. 



In limestone, used for railroad ballast, we had 8 holes, spaced 18 

 feet apart. Average face burden 19 feet; average depth 48 feet; approxi- 

 mately 4,900 cubic yards. There were used 3,300 pounds 40 per cent 

 dynamite, making a cost per cubic yard of about .084 cents. 



A blast in cement rock, 9 holes, spaced 22 feet apart. Average face 

 burden 32 feet; average depth of hole 62 feet; approximately 13,000 cubic 

 yards. For this there was used 2,500 pounds 60 per cent and 1,800 pounds 

 40 per cent dynamite, making a cost of about .046 cents per cubic yard. 



Another blast in cement rock of 7 holes, spaced 15 feet apart. Average 

 face burden 23 feet; depth 60 feet; about 5,400 cubic yards. For this there 

 was used 500 pounds 60 per cent and 2,900 pounds 40 per cent dynamite, 

 making a cost of about 8 cents per cubic yard. 



Blast in hard, massive limestone, 8 holes. Average space between 

 about 28 feet; average face burden 33 feet; depth of holes about 95 feet; 

 approximately 26,000 cubic yards. For this there was used 2,200 pounds 

 blasting gelatin, 3,350 pounds 60 per cent and 1,250 pounds 40 per cent 

 dynamite, making a cost per cubic yard of about .046 cents. 



Blast in limestone for lime manufacturing of 3 holes, spaced about 17 

 feet apart. Average face burden 24 feet; average depth of holes 100 feet; 

 approximately 4,600 cubic yards. The dynamite used amounted to 1,200 

 pounds, 60 per cent and 1,600 pounds 40 per cent making an average cost 

 of .082 cents. 



Another blast in limestone for cement manufacture, 9 holes, spaced about 

 20 feet apart. Average face burden 36 feet, and about 53 feet in depth; 

 approximately 12,700 cubic yards. For this there was used 1,720 pounds 

 60 per cent and 2,500 pounds 40 per cent, making a cost of .045 cents per 

 cubic yard. 



Another blast consisting of 4 holes 18 feet apart with about 25 feet face 

 burden and 100 feet deep; approximately 6,700 cubic yards, for which there 

 was used 1,200 pounds 60 per cent and 1,600 pounds 40 per cent, making 

 an average cost of .056 cents per cubic yard. 



Eight holes blast spaced 15 feet apart, with a face burden of approxi- 

 mately 25 feet, holes 115 feet deep; about 12,800 cubic yards, for which was 



