96 F. LOEWINSON-LESSING 



Let us examine each of these considerations separately. 



1. Protoclastic structure is not characteristic of all anorthosites 

 (see those of Kiev and the Baikal). This structure can be explained 

 in certain cases by the action of mineralizers (cf . my considerations 

 on the origin and the effect of zoisite in the anorthosites of Syysertsk 

 in the Oural Mountains).^ Furthermore protoclastic structure is 

 wanting in pyroxenites and dunites, these latter being characterized 

 by a special structure, indicative of the process I call magmatic auto- 

 catalysis. 



2. Should it really be proved that the monomineral igneous rocks 

 do not occur in dikes, this fact by itself would not be a sufficient 

 proof against their existence in the liquid state. The great viscosity 

 of such simple magmas is a sufficient cause for their being incapable 

 of forming small intrusions. But the absence of dikes in the group 

 of the monomineral rocks is not at all an irrefutable statement, for 

 pyroxenites and dunites often occur in this form. Rosenbusch and 

 Daly even assume that the dike form is usual for pyroxenites. Of 

 course Rosenbusch {Elemente der Gesteinslehre) is not correct in as- 

 suming that pyroxenites and peridotites occur only in dikes ; the 

 large intrusive masses of pyroxenites in the Blue Mountains near 

 Barantcha (Oural) ,^ the pyroxenites and dunites of the Denejkin 

 Kamen,^ and other localities in the Oural Mountains are in contra- 

 diction with this assertion. 



Certain feldspathic rocks occur also in the dike form, for example, 

 the albitites. In the region of the Canadian anorthosites Adams 

 cites dikes. On the other hand, we may ask: Do gabbros (except 

 beerbachite and gabbroporphyrite) or nephehte syenite often occur 

 in this form ? 



' F. Loewinson-Lessing, "On the Most Southern Deposit of Platinum in the Oural," 

 Annates de I'Inst. Polytechn. St. Petersb., Vol. XIII (1910). 



^ Th. Tschernyschew, "Le Chemin de far dans les Limites les districts miniers de 

 Taguil et de Goroblagadat," Guide des Exeurs., Congr. Geol. St. Petersburg, 1897. 



F. Loewinson-Lessing, "A New Locality of Platinum Deposits (in the Blue 

 Mountains, near Barantcha, Oural)." Annals I'Inst. Polytechn. St. Petersburg. 1909. 

 Vol. XI. 



3 F. Loewinson-Lessing, "Geologische Skizze der Besitzung Jushno-Saasersk und 

 des Berges Denejkin Kamen im nordl. Ural." Trav. d.l. Soc.d. Natur. St. Petersburg, 

 1900. In this monograph I have described and figured a series of very manifold banded 

 gabbros. Grout does not cite me in his paper on banded structures as he evidently 

 does not know my book. 



