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Essentials for the Microscopical Determination of 

 Roci{-forming Minerals and Rocks 



By ALBERT JOHANNSEN 



Professor of Petrology 

 The University of Chicago 



A laboratory manual designed to provide students of petrology and geologists 

 interested in petrology with information on methods of determining microscopically 

 the points of separation between similar minerals and their modes of occurrence. 



This valuable volume contains, in addition to a folding alphabetical list so 

 placed that reference may be made to it without turning pages, the following 

 important features: "A Quantitative Mineralogical Classification of Igneous 

 Rocks" ; "A Summary of Petrographic Methods" ; "Modes of Occurrence of Various 

 Minerals"; "Rules for Computing Rocks from Their Modes"; and "Names Pro- 

 posed for Various Families." 



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