CLASSIFICATION OF IGNEOUS ROCKS 165 



amount of mafic minerals. There are many subfamilies, depending 

 upon the accessories or dark constituents. 



Granitite. This is an old term which has been used with 

 a great variety of meanings. So long ago as 1823 von Leonhard^ 

 said that the proposal to call granites with accessory minerals 

 granitite was superfluous and unfitting. Rose^ used the word for 

 muscovite-free biotite-bearing rocks with quartz, orthoclase, and 

 considerable oHgoclase. It was used in the same sense by Senft^ 

 and Rosenbusch,'' and is here also used as a synonym for biotite- 

 granite. Cathrein's^ suggestion that it be used for plagioclase-rich 

 hornblende-bearing granites has never been followed. 



Amphibole-granite. 



Arfvedsonite-granite Brogger.^ 



Augite-granite. 



Binary-granite Keyes^ contains both muscovite and 

 biotite. It is also called two-mica granite. 



Hypersthene-granite. 



Syn. : Charnockite Holland.^ 



Microcline-granite . 



Muscovite-granite . 



Tourmaline-granite, etc. 



Rhyolite von Richthofen. The name rhyolite (from 



pha^, "lava stream," "torrent") was given by von Richthofen' to 



the extrusive equivalent of granite on account of its usual fluidal 



'K, C. von Leonhard, Charakteristik der Felsarten (Heidelberg, 1823), I, 54. 



^ Gustav Rose, "Ueber die zur Granitgruppe gehorenden Gebirgsarten," Zeitschr. 



d. d. geol. Ges., I (1849), 386; also pp. 363-66. 



3 Ferdinand Senft, Classification und Beschreihung der Felsarten (Breslau, 1857), 

 p. 297. 



" H. Rosenbusch, Mikroskopische Pkysiograpkie der massigen Gesteine (ist ed.; 

 Stuttgart, 1877), II, 20-21. 



5 A. Cathrein, "Zur DiinnschlifFsammlung der Tiroler Eruptivgesteine," Neues 

 Jahrh., I (1890), 72. 



' W. C. Brogger, "Die Mineralien der Syenitpegmatitgange der sudnorwegischen 

 Augit- und Nephelinsyenite," Zeit.f. Kryst., XVI (1890), 68. 



7 Charles Rollin Keyes, "Origin and Relations of Central Maryland Granites," 

 U.S. Geol. Stirv., Ann. Kept., XV (1895), 714. 



8T. H. Holland, "The Charnockite Series, a Group of Archean Hypersthenic 

 Rocks in Peninsular India," Mem. Geol. Surv. India, XXVII (1900), 2, 119. 



"Ferdmand Freiherrn v. Richthofen, "Studien aus den ungarisch-siebenburgeri- 

 schen Trachytgebirgen," Jahrb. d. k. k. geol. Reichsanst., XI (i860), 156. 



