THE MINERALOGY AND PETROLOGY OF INTRUSIVE TRI- 

 ASSIC DIABASE AT GOOSE CREEK, LOUDOUN COUNTY, 

 VIRGINIA. 



By Earl V. Shannon, 



Assistant Curator of Geology, United States National Museum. 



INTRODUCTION. 



The present paper records observations made on several trips to 

 the Goose Creek trap quarry, together with the results of a large 

 amount of office and laboratory study of the specimens collected. 

 The data thus acquired have become somewhat voluminous and, since 

 other duties are forcing attention, it is considered best to present the 

 results thus far attained while they are fresh in mind. My work does 

 not by any means exhaust the locality but merely serves as a start- 

 ing point from which study of the interesting features may be con- 

 tinued. The locality is a pleasant journey from Washington and is 

 recommended to any petrologist or mineralogist seeking an educa- 

 tional day's outing in the field to relieve the monotony of office 

 routine. 



ACKNOWLEDGMENTS. 



I have enjoyed an unusual amount of cooperation in preparing 

 this paper and it seems appropriate to make some acknowledgments. 

 For the suggestion that the locahty would be found worthy of study 

 I have to thank Dr. George P. Merrill. One of my visits to the 

 quarry was made in company with the following members of the 

 Mineralogical Society of Washington: W. F. Foshag, W. S. Burbank, 

 Frank L. Hess, Esper S. Larsen, jr,, Clarence S. Ross, Edward Samp- 

 son, Waldemar T. Schaller, Edgar T. Wherry, and Ralph W. G. 

 Wyckoff. Observations and opinions of all of these men and speci- 

 mens collected by them have been at my disposal. In addition to 

 the help of the above scientists, various points have been discussed 

 with Dr. Norman L. Bowen, who has pointed out similarities to his 

 Gowganda Lake area, and with Drs. Herbert E. Merwin and Clarence 

 N. Fenner, who are familiar with the locality. I have especially to 

 thank Drs. Esper S. Larsen and Clarence S. Ross for constant advice 



No. 2539. — Proceedings U. S. National Museum. Vol. 66, Art. 2. 



94110—24 1 



