Page:The Journal of geology (IA journalofgeology11893univers).pdf/12

The macroscopic examination of the rocks of this type continued 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 (granistone of Cocchi and other Italians), with labradorite or saussurite and diallage, or saussurite and smaragdite (gabbro of Cocchi, Hunt and others); cuphotides, 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 varieties that had been separated as distinct sub-groups of the general 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 selbständiger Gementheil des Gabbro, und es werden daher durch ihre Anwesenheit keine besonderen Abänderungen erzielt." It is fibrous and is intergrown with the augite and diallage. The labradorite is saussuritized (p. 935) and the saussurite is therefore regarded as an unessential component. The hornblende-gabbros and the saussurite gabbros of the Harz