UNIVERSITY OF CALIFORNIA PUBLICATIONS 

 Bulletin of the Department of Geology 



Vol. 3, No. 8, pp. 219-229. ANDREW C. LAWSON, Editor 



PLUMASITE 



AN OLIGOCLASE-CORUNDUM ROCK 



NEAR 



SPANISH PEAK, CALIFORNIA 



BY 



Andrew C. Lawson. 



CONTENTS. 



PAGE 



Recent Recognition of Corundiferous Rocks 219 



The Discovery 221 



The Peridotite Cut by Corundiferous Dyke 222 



Chemical Composition of Peridotite 224 



Original Edenite 225 



Extent of Corundiferous Dyke 225 



The Corundiferous Facies 225 



The Corundum 226 



Chemical Composition of the Rock 227 



The Rock Type Defined 227 



Other Facies of the Dyke 228 



Correlation 229 



Recent Recognition of Corundiferous Rocks. — One of the 

 notable features of petrographie research during the past few 



years has been the discovery in several widely separated portions 

 of the earth's surface of rocks in which the mineral corundum 

 plays the role of a normal constituent. The mineral has long 

 been known as an interesting accessory in certain granite rocks 

 and as a not uncommon occurrence in certain metamorphic 

 schists and crystalline limestones. But the interest attaching to 

 these occurrences has been almost purely mineralogical , and they 

 have contributed but little to petrological science. Even in the 

 latest text-books corundiferous igneous rocks are not discussed. 

 In the last edition of Iddings' translation of Rosenbusch's 

 " Mikroskopische Physiographie," 1898, it is asserted that 



