642 PETROLOGICAL ABSTRACTS AND REVIEWS 



Richardson, W. Alfred. "A New Model Rotating-Stage Petro- 

 logical Microscope." Mineralog. Mag., XIX (1920), 96-98. 

 Describes a new Swift petrographic microscope. 



RiCHARZ, Stephan. "Die Basalte der Oberpfalz," Zeitschr. d. 

 deutsch. geol. GeselL, LXXII (1920), i-ioo. PI. 2, Figs. 8. 

 The basalts of the Oberpfalz are very similar megascopically, but 

 under the miscroscope three types are recognized; pure nephelite- 

 basalts, pure feldspar-basalts, and nephelite-bearing feldspar-basalts. 

 No melihte-basalts were found although they occur at Steinberg near 

 Hohenberg in Oberfranken. Some of the basalts are rich in both endo- 

 genic and exogenic inclusions, others rarely contain any. Among the 

 inclusions are olivinefels, pyroxenites, fritted sandstones, and basalt- 

 jaspis. In addition to the usual minerals, labradorite, nephelite, augite, 

 olivine, magnetite, some glass, there occurs in some of these rocks, 

 biotite. In the inclusions aegirite, katophorite, sanidine, oligoclase- 

 andesine, quartz, and the recrystaUization minerals, natrolite, phillipsite, 

 calcite, aragonite, opal, and a new mineral called magnalite, occur. 

 Field observations show that the basalt occurs in the form of dikes much 

 more commonly than previously thought. The width varies from 50 

 to 200 meters. 



RiNNE, F. Gesteinskunde. Leipzig, 1921. 6th and 7th (double) 

 ed., 8vo. Pp. 365, Figs. 510. 



It is almost impossible in a short review to do justice to a general 

 textbook which does not aim to present any startling new theories. 

 One can do little more than give a summary of the table of contents. 

 The first 120 pages of this book, which is not only a petrography but a 

 petrology, are devoted to general geological modes of occurrence of igneous 

 rocks, sediments, and crystalline schists, jointing, parting, and other 

 structures, petrographic methods, and the mineral constituents of the 

 rocks. The final 235 pages are devoted to descriptive petrography of 

 igneous, metamorphic, and sedimentary rocks. As an introduction to 

 the igneous rocks there are thirty-eight pages devoted to their chemical 

 composition and modes of expressing these graphically, differentiation, 

 gases in magmas, sequence of crystallization with many diagrams, and 

 textures and structures. Following the general descriptions of the 

 igneous rocks are a few pages on meteorites. Introducing the sedi- 

 mentaries are sections on origin, weathering, transportation, deposition, 



