438 THE JOURNAL OF GEOLOGY. 



The macroscopic examination of the rocks of this type con- 

 tinued to give rise to many different methods of classifying 

 them, but the general tendency after this time seems to have 

 been toward the union of the gabbros and the hypersthenites 

 into one group. Von Cotta, 1 for instance, embraces the gabbros 

 hypersthenites and norites under the single head "gabbro," 2 and 

 then divides this group into five sub-groups — gabbros (grani- 

 tone of Cocchi and other Italians), with labradorite or saussurite 

 and diallage, or saussurite and smaragdite (gabbro of Cocchi, 

 Hunt and others); euphotides, equivalent to the saussuritized 

 gabbros of later authors ; norites of Scheerer, which are 

 regarded as gabbros containing a soda-orthoclase and some 

 quartz ; hypersthenites, consisting of plagioclase and hypersthene, 

 and finally, Monzoni- hypersthenites, afterwards discovered by 

 de Lapparent 3 to belong to an entirely different group since 

 they contain no hypersthene. 



In the same year in which von Cotta's classification appeared 

 Aug. Streng 4 began the task of reducing the number of varie- 

 ties that had been separated as distinct sub - groups of the gene- 

 ral group gabbro. In his article on the gabbros and associated 

 rocks in the Harz he describes the former as made up of 

 labradorite, diallage, hypersthene, augite, hornblende, brown 

 mica, and ilmenite. Of the hornblendic constituent he says, it 

 is " Kein selbstandiger Gementheil des Gabbro, und es werden 

 daher durch ihre Anwesenheit keine besonderen Abanderungen 

 erzielt." It is fibrous and is intergrown with the augite and dial- 

 lage. The labradorite is saussuritized (p. 935) and the saus- 

 surite is therefore regarded as an unessential component. 

 The hornblende -gabbros and the saussurite gabbros of the Harz 



T Die Gesteinslehre. 2, Aufl. Freiberg, 1862. 



2 Cf . also Rocks Classified and Described. A Treatise on Lithology. By Bernhard 

 von Cotta. An English edition by P. H. Lawrence, London, 1866. 



3 de Lapparent: Sur la constitution geologique du Tyrol meridional. Annales 

 des Mines. (6) VI., 1864, p. 259. 



4 Aug. Streng : Ueber Gabbro und den sogenannten Schillerfels der Harzes. 

 Neues Jahrb. F. Min., etc. 1862, p. 932. 



