CLASSIFICATION OF IGNEOUS ROCKS 171 



There are many varieties of syenite, depending upon the char- 

 acter of the dark or accessory constituents. 



Biotite syenite. 



Syn. : Syenitite Loewinson-Lessing/ analogous to 

 granitite for biotite-granite. Polenov,^ however, had previously 

 used the term in a different sense, namely for syenite-aplite. 



Hornblende-syenite. 



Arf vedsonite-sy enite . 



Augite-syenite. 



Epidote-syenite . 



Pyroxene-syenite. 



Hj^ersthene-syenite (Syn.: Mangerite), etc. 



Trachyte Hauy. The term trachyte, from the Greek 

 Tpaxvs, on account of the rough appearance of the rock, was intro- 

 duced by Haiiy^ in his lectures at the Jardin des Plantes to char- 

 acterize the rocks from the Drachenfels on the Rhine. Although 

 the feldspar in these rocks had previously been determined and 

 named sanidine by Nose,'' yet plagioclase rocks of the general 

 appearance of the original trachyte came to be included in the term. 

 Later, von Buch^ separated certain Andean extrusives with plagio- 

 clase from this group and called them andesites. At the present 

 time trachyte is used for the extrusive equivalents of syenite, that 

 is, for rocks consisting of potash-feldspar, a little plagioclase, and a 

 biopyribole. Many trachytes are orthotrachytes (2 in). 

 (2213) Monzonite De Lapparent-Brogger. The principal 

 rock of Monzoni, in the Tyrol, is of quite variable character. It 



' F. Loewinson-Lessing, "Kritische Beitrage zur Systematik der Eruptivgesteine, 

 II," Tscherm. Min. Petr. Mitth., XIX" (1900), 173. 



^ B. Polenov, "Die massigen Gesteine von nordlichen Theile des Witim-Plateau," 

 Travaux de la Societe Imperiale des NaturaUstes de St. Petersbourg, XXVII (1899), 

 livr. 5, 464. 



3 Haiiy did not publish the name until 1822 in his Traite de mineralogie (2d ed.; 

 Paris, 1822), IV, 579, but it was accredited to him as far back as 1813 in Alexandre 

 Brongniart's "Essai d'une classification mineralogique des roches melangees," Jour, 

 d. Mines, XXXIV (1813), 43- 



'' K. W. Nose, Orographische Brief e, I, 26, 113. 



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

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



