550 WATSON AND WHERRY: PYROLUSITE FROM VIRGINIA 



GEOLOGY AND MmEUALOGY .—Pyrolusite from Virginia. 

 Thomas L. Watson, University of Virginia, and Edgar T. 

 Wherry, Bureau of Chemistry. 



PART I. GEOLOGY 



Much of the manganese ore mined at Powells Fort on north- 

 east Massanutten Mountain 6 miles north of east of Woodstock, 

 Shenandoah County, Virginia, is crystalline in structure and 

 of a high degree of purity. Prior to mining operations by the 

 present company, the Stockwood Realty Corporation, the mine 

 had been worked at different times for a long period of years, 

 and the ore shipped was described as being remarkably clean and 

 a high grade of soft crystallized pyrolusite. Crystals of the man- 

 ganese mineral ranging up to more than a millimeter across are 

 plentiful and are more abundant than at any other manganese 

 mine known to the writer. 



During the course of recent field investigations of Virginia 

 manganese deposits for the State Geological Survey, collections of 

 both the crystals and crystalline mineral were made by the writer 

 for laboratory study. Specimens of the crystals were submitted 

 to Doctor Edgar T. Wherry, of the Bureau of Chemistry, United 

 States Department of Agriculture, Washington, D. C, for 

 crystallographic study, the results of which form Part II of this 

 paper. 



In the known deposits of manganese-oxide ores of the southeast 

 Atlantic states, the important ore minerals are usually given as 

 psilomelane, pyrolusite, manganite, and wad. Braunite, which 

 is reported to be a characteristic mineral in association with 

 psilomelane in the Arkansas deposits, has not, so far as the writer 

 is aware, been definitely identified, in the manganese deposits 

 of the southeastern Atlantic states. In their principal occur- 

 rences two or more of these minerals are usually intimately asso- 

 ciated, the most common being probably psilomelane and pyrolu- 

 site. The manganese-oxide mineral occurring in crystal form in 

 these deposits has been regarded by some as pyrolusite, and by 

 others as manganite. Both may be present, but their identifica- 

 tion has been based almost without exception on a few physical 



