CLASSIFICATION OF IGNEOUS ROCKS 213 



it to rocks consisting of "Saussurit oder Jade und Smaragdit, oder 

 haufiger aus Feldspath und Smaragdit .... oder auch seltener 

 aus alien diesen Substanzen vereinigt." His saussurite is altered 

 feldspar, the jade amphibole, and the smaragdite probably green 

 diallage. For a long time the name continued to be applied to 

 plagioclase-diallage rocks, but in recent years the kind of pyroxene 

 has been disregarded, and only the basic character of the plagioclase 

 has been considered essential to the definition. In the present 

 classification, therefore, gabbro is simply a rock consisting essen- 

 tially of labradorite or bytownite and a biopyribole. Olivine may 

 be an accessory, and magnetite is usually present in variable 

 amounts. The orthoclase-gabbro of Streng^ and Irving^ is really 

 diallage-monzonite or monzodiorite. 



Hornblende-gabbro . 



Olivine-gabbro. 



Quartz-gabbro. 



Uralite-gabbro, etc. 



Norite Esmark. Esmark^ applied the name norite 

 to certain Norwegian rocks which belong in part to the rocks now 

 called norites, but in part to the diorites. Scheerer" appHed it 

 to rocks related to the gabbros and hyperites. Rosenbusch^ 

 limited it to rocks containing essential hypersthene and plagioclase, 

 and said that unless so Hmited the term would be meaningless, and 

 later^ gave the constituents as basic plagioclase and an orthorhombic 

 pyroxene. In this sense it is now generally used. 



Hyperite Tornebohm. These rocks, intermediate 

 between gabbros and norites, and containing both orthorhombic 

 and monoclinic pyroxenes, were originally called hypersthenites 



^Aug. Streng, "Uber die kristallinischen Gesteine von Minnesota in Nord- 

 amerika," N'eiies Jahrb. (1877), pp. 113-38. 



^ Roland Duer Irving, "The Copper-bearing Rocks of Lake Superior," U.S. Geol. 

 Surv., Mono. 5 (1883), pp. 50-52. 



3 Esmark, MagasinfUr Naturvidenskaberne, I, 207. 



"Th. Scheerer, Gaea Norvegica, Heft ii, 313; also " Geognostisch-mineralogische 

 Skizzen gesammelt auf einer Reise an der Slid-Kuste Norwegens," Neues Jahrb. 

 (iS43),p.668. 



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

 Stuttgart, 1877), p. 477. 



^ Ibid. (4th ed., 1907), p. 348. 



