PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 509 



Gabliro. Diabase.] 



No. 715. GABBRO (vnthenstatiHeamdolivine), 



"From an island in Poplar lake, near the portage coming from Little lake. The usual rock about Poplar 

 lake." Probably near the centre of the west side of sec. 7, T. 04-1 W. 

 Ref. Annual Report, x, page 85; Bulletin ii, page 91. 



Meg. The rock is closely similar to No. 714, except that this specimen (No. 

 715) is a little coarser grained than the other. 



Mic. M. E. Waclsworth's description of this rock is as follows:* 



' Is a grayish granular rock, composed of plagioclase, some olicinc and pi/i-twin-, 

 part of which has the cleavage and optical characters of <-nxl<iti1<' and part that of 

 diallage." 



No section found. 



Ai/e. Cahotian. IT. s. G. 



No. 716. DIABASE (n-it/i <>rtlioc./iiK>; </i/</,lz uml 



Prom the top of Stair portage, between Mud and Duncan's lakes; N. W. J4 sec. 27, T. 65-1 W. 

 Ref. Annual Report, x, page 85; Bulletin ii, pages 115, 117. 



A medium-grained, greenish-gray rock, composed of white feldspar, 

 hornblende and magnetite. 



Mic. M. E. Waclsworth's description of this rock is as follows:! 



" A greenish-gray crystalline rock, somewhat altered, macroscopically, while the 

 section shows that it is miscroscopically a much altered specimen. Some of the 

 iiiii/iti' is distinguishable, but most of it is nearly or entirely altered to n'ritlitc and 

 (ji-i'di hornblende, part of which, "however, is stained brown. The feldspar is also 

 much changed to the common dirty white kaolin-like substance, while its clear 

 spaces are replaced by secondary ijiiaiiz, ni-fhoclaNe, and j>l<it/ii>cl<txe. Considerable 

 ii/iufifi', Itiotite and magnetite occur." 



The texture of the section is markedly diabasic, the augite having an ophitic 

 relation to the feldspar. 



One section examined. 



At/t'. Cabotian. u. s. G. 



No. 717. DlARASR (icitli i/ninin un/l /ior/ili/<-n<J<>). 



North side of South lake opposite the east line of sec. 24, T. G5-2 W. 

 Ref. Annual Report, x, page 85; Bulletin ii, pages 114 110. 



Mr;/. A very dark-gray rock, rather fine grained and composed largely of 

 feldspar, augite and hornblende. 



Mir. M. E. Wadsworth's description of this section is as follows::}: 

 " The section shows that the rock has been much altered. Part of the original 

 i', inii/iti' and iiiiii/i/ftiti' remain intact, but much of the augite has been replaced 



liutlelin ii, p. 91. 



\Hllllrtill ii, p. 117. 



\BulMin ii, pp. 114, 115. 



