255 



1:3:7; Na,0, 6'10 ; K L ,0, 0'34 ; Sp. Gr. 2'69). Bulk analysis Si0 2 66'91 

 AJ 2 3 , 15-20; FeO, 6'45; MgO, 2'35; CaO, 073; Na 2 0, 3'33 ; K 0, -86; 

 H 2 0-16; total 98-99; Sp. Gr. 2724. The rock is thoroughly granitic in 

 texture. The specimen analysed contained a large amount of quartz. 

 Professor BONNEY (I) has proposed that the name tonalite should be used 

 generally instead of quartz-diorite. 



Banatite. This name was applied by VON COTTA to certain rocks 

 occurring in the province of Banat in Hungary. They are intrusive in rocks 

 as late as the Cretaceous. Similar rocks occur in the Schemnitz district/ 2 ) 



The Schemnitz rocks have been variously termed greenstone- 

 trachyte, syenite, diorite and propylite by different authors. According 

 to ROSENBUSCH they vary in character between quartz-diorites (tonalites), 

 quartz-augite-diorites, diorites and augite-diorites. Quartz is generally 

 present ; the amount of augite varies in different specimens from one 

 and the same locality. The hornblende is either brown or green. The 

 biotite in its original condition is always brown, but owing to alteration it 

 is frequently seen to consist of alternating brown and green layers. 

 Hypersthene is occasional!} 7 present. The plagioclase belongs to the 

 andesine-labradorite series. It contains glass and liquid inclusions. The 

 quartz is rich in liquid inclusions. Sphene and zircon occur as accessories; 

 epidote, calcite and uralitic hornblende as secondary constituents. Owing 

 to alteration the rocks assume the so-called propylitic or greenstone-like 

 aspect. They have a silica percentage of from 60 to 65, and a specific 

 gravity varying from 2'6 to 27. In structure, composition and mode of 

 occurrence they may be regarded as typical diorites in the sense in which 

 that term is employed in the present work ; in other words they are the 

 hypogene representatives of the mica-, hornblende- and augite-andesites. 



Propylite. This name was introduced by RICHTOFEN for rocks of the 

 above group occurring near Schemnitz and was subsequently extended 

 by him to similar rocks occurring in the Washoe district of North America. 

 It was believed for some time that these rocks were the earliest eruptive 

 rocks of the Tertiary period and considerable interest attached to them 

 on that account. It is now generally recognized that this view was 

 incorrect and the term propylite has almost disappeared from petro- 

 graphical literature. The special features of the group are now recognized 

 as being due partly to the conditions of consolidation (plutonic) and partly 

 to subsequent alteration. 



Quartz-norite. A very interesting group of eruptive rocks of inter- 

 mediate composition occurs in the neighbourhood of Klausen in the Tyrol. 

 They are well exposed in the valleys of the Tinnebach and its tributaries the 

 Rothbach and the Vildar. The general term diorite has been used for these 

 rocks. TELLER and VON JOHN rs) have shown that they are composed essenti- 

 ally of plagioclase, hypersthene, enstatite, augite (including diallage), biotite, 

 quartz, magnetite and apatite. The felspar gives lath-shaped sections. 



(1) Q. J. G. S., Vol. XLL, Proc. p. 73. 



(2) See JUDD on the ancient volcano of the district of Schemnit/. Q. J. G. S Vol 

 XXXII. (187o), p. 292. 



(3) J. G. R., 1832, XXXII., p. 589. 



