CLASSIFICATION OF IGNEOUS ROCKS 175 



containing plagioclase as well. See note under trachyte (2212). 

 In 1835 von Buch' described certain volcanic rocks from the Andes, 

 consisting of plagioclase (originally thought to be albite) and horn- 

 blende. He named them andesites. Later the term was appHed 

 to oligoclase- or andesine-bearing rocks, and it is used in this sense 

 here. The dark mineral may be biotite, hornblende, or augite, or 

 combinations of these, which thus give subfamihes. 



Biotite-andesite. 



Mica-andesite. 



Hornblende-andesite . 



Syn. : Hungarite Lang,^ named from their wide dis- 

 tribution in Hungary. 



Augite-andesite. See note under basalt (2315). 



Hypersthene-andesite Becke.^ 



Syn.: Santorinite Becke. Becke'' proposed the 

 term santorinite for acid- and alboranite for basic rocks of Santorin. 

 The former are h5rpersthene-andesites rich in soda (Na:Ca>2). 

 The phenocrysts are labradorite with mantles of oHgoclase, while 

 the groundmass is acid oligoclase. The average feldspar, therefore, 

 is acidic. Washington^ had previously called the acid rocks 

 pyroxene-andesites and had proposed the term santorinite for the 

 members carrying basic plagioclase. Santorinite, used with two 

 meanings, should therefore be abandoned. 



(2217) Nephelite- (leucite-) bearing syenite. 



(2218) Nephelite- (leucite-) bearing monzonite. 



(2219) Nephelite- (leucite-) bearing monzodiorite. 



(2220) Nephelite- (leucite-) bearing diorite. 



(2222) Nephelite-syenite RosENBUSCH. Rosenbusch^ included, 



'Leopold von Buch, "Ueber Erhebungscratere und Vulcane" (read in Berlin 

 Akad., March 26, 1835), Pogg. Ann., XXXVII (1836), 190. 



2 Heinr. Otto Lang, Grundriss der Gesieinskunde (Leipzig, 1877), p. 196. 



3 F. Becke, "Der Hypersthen-Andesit der Insel Alboran," Tscherm. Min. Petr. 

 Mitth., XVIII (1899), 553. 



4 Ibid., p. 553. 



s Henry S. Washington, "Italian Petrological Sketches: V. Summary and Con- 

 clusions," Jour. GeoL, V (1897), 368. 



^H. Rosenbusch, Mikroskopische Physiographie der massigen Gesteine (ist ed.; 

 Stuttgart, 1877), 11, 204. 



