Shaft sinking by diamond drilling, Bellefonte mine, National Gypsum Co., Centre County, Pa.

Author:	Mosier, McHenry.
Year:	1948
Document Type:	USBI
Issuing Agency:	U.S. Dept. of the Interior, Bureau of Mines,
SUDOC:	I 28.27:7477
Series:	Information circular / United States Department of the Interior, Bureau of Mines ;
Report Number:	7477
Subjects:	Rock-drills
	Shaft sinking--Equipment and supplies
Link:	https://hdl.handle.net/2027/mdp.39015078463422