BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 

 Vol. 7, pp. 95-134 December 20, 1895 



SYENITE-GNEISS (LEOPARD ROCK) FROM THE APATITE 

 REGION OF OTTAWA COUNTY, CANADA* 



BY C. H. GORDON 



(Presented before the Society August 28, 1895) 

 CONTENTS 



Page 

 Introduction 95 



General description of the region 96 



Geology of the region 96 



Character and classification of the rocks 96 



Lithological characters 98 



High Rock district 98 



General description 98 



Geological structure 99 



Subdivisions of the syenite-gneiss 99 



Geological occurrence of the rock. 100 



Megascopical characters 103 



Coarse syenite-gneiss 103 



Ellipsoidal syenite-gneiss 105 



Streaked syenite-gneiss 106 



Microscopical description 107 



Coarse syenite-gneiss 107 



Ellipsoidal syenite-gneiss or leopard rock 114 



Streaked syenite-gneiss 117 



Character and relations of the rocks 119 



Nomenclature 120 



Origin of the ellipsoidal structure 123 



General hypotheses 123 



Primary origin 124 



Differentiation of the coarse syenite 124 



Differentiation of the ellipsoidal rock 125 



* Condensation of thesis presented for degree of Doctor of Philosophy, University of Chicago, 

 June 13, 1895. 



The author is indebted to Dr A. R. C. Selwyn and his associates on the Canadian Geological 

 Survey and to Mr A. P. Twidale, superintendent of the High Rock phosphate mine, for numerous 

 courtesies and favors. The analyses were made by Professor William Hoskins, of the Chicago 

 Academy of Sciences. Especial acknowledgments are made to Professor J. P. Iddings for his 

 keen, critical analysis and painstaking assistance. Without his aid tlie paper would lack much of 

 any value it may possess. 



XIV— Bull. Geol. Soc. Am., Vol. 7, 1895. (95) 



