24 AUSTRALASIAN ANTARCTIC EXPEDITION. 



significance may have real use, and we have used the term " gneiss " as a general rock 

 name for members of the crystalline schists which have no special name and which 

 may or may not possess a schistose structure ; for example, a certain rock has been 

 styled pyroxene granulite by the Germans, pyroxene gneiss by the French, and a norite 

 by the Indian Geological Survey. We do not use the term " pyroxene granulite " 

 because the granulitic structure is a very common structure in almost all classes of the 

 crystalline schists. We do not use the term " norite " because it is applied to a special 

 variety of igneous rocks. We apply the term gneiss in each case, and distinguish as a 

 plagioclase-pyroxene-gneiss, or a pyroxene-alkali-felspar-gneiss, in spite of the fact that 

 no schistosity may be evident. 



As we make large use of the term " amphibolite " we quote the following from 

 L. Henzer * : " By older writers a pure amphibole rock is occasionally called 

 amphibolite, while the garnet-amphibolites, felspar-amphibolites, or zoisite-amphibolites 

 were called amphibole schists, greenstone, hornfels, etc. According to Zirkel, the 

 typical amphibolite consists only of hornblende. Chiefly through Rosenbusch the 

 term has become firmly established in the literature in recent years. Rock types with 

 amphibole as their main constituents (hornblende-schists or hornblende-fels and 

 actinolite schists) are distinguished from the actual amphibolite whose mineral content 

 is essentially hornblende and plagioclase, though the latter can be replaced partly or 

 wholly by zoisite, epidote, garnet, or scapolite." This is the usage which has been 

 adopted by Grubenmann and which gives the term amphibolite a precise chemical and 

 mineralogical meaning. 



The need of the general term, which we supply for ourselves in the term " gneiss," 

 is evidenced in a paper published by Loewinson-Lessingf in 1905, which discusses the 

 classification and nomenclature of the amphibole rocks belonging to the crystalline 

 schists. In the study of the crystalline schists of the River Tagil, in the Middle Urals, 

 Loewinson-Lessing was struck with the close connection between the schistose and 

 massive members of the crystalline schists. He found massive schlieren in the midst 

 of schistose rocks and argued that the term " schist " was scarcely fitting for the non- 

 schistose rocks. But he meets his difficulty by introducing terms which emphasise the 

 likeness of the massive types to igneous rocks e.g., paradiorite, amphibole, para- 

 gabbro, etc. These terms obscure the observed close connection of these rocks with 

 the crystalline schists. They unduly accentuate differences which have no genetic 

 bearing and place them equivalent with characters which do have genetic meaning. 

 But yet they are intended to limit and add precision to the term " amphibolite." An 

 amphibolite, according to Loewinson-Lessing, is a rock whose essential constituent is 

 amphibole alone. This violates the conclusion expressed in the preceding quotation 

 from a paper to which Loewinson-Lessing makes no reference. A rock composed 

 of amphibole and plagioclase is called " paradiorite " or " amphibole para-gabbro " if 



* " Bin Beitrag zur Kenntnis der Eklogite und Amphibolite," Laura Hezner, Wien, 1903, p. 5. 



t " Ueber Klassifikation und Nomenklatur der zur Formation der Kristallinischen Schiefer gehorigen Amphibolgesteine," 

 von F. Loewinson-Lessing, Centralblatt Mineralogie Geologie, 1905, p. 407. 



