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PHYSICAL GEOLOGY 



-4. Anorthosite, all feldspar. 



B. Syenite, mostly feldspar. 



C. Diorite, some feldspar. 



. Peridotite, no feldspar. 



FIG. 10. Contrast of feldspathic and ferromagnesian rocks. 

 (Pirssoa, Rocks and Rock Minerals.) 



