110 



Transactions. 



Art. X. — The Scheelite of Otago. 



By A. M. Finlayson, M.Sc. 



Communicated by Dr. Marshall. 



[Read before the Otago Institute, 8th October, 1907.] 



Plate XVI. 



Scheelite occurs in greater or less quantity in a large number 

 of the auriferous- quartz veins in the Otago goldfields. The 

 country rock of the veins is for the most part a quartzose mica- 

 schist, graduating into phyllite and slate. It is included in 

 Sir James Hector's " foliated schists,"* and in the Wanaka 

 and Kakanui series of the late Captain Hutton.f 



Only those veins which carry scheelite in exploitable quantity 

 will here be considered, and these may be conveniently grouped 

 into two classes — (1) fissure- veins ; (2) bedded or segregated 

 veins. The latter occur exclusively in the Macrae's district ; 

 the former class includes all other known scheelite-veins. 



(1.) Fissure-veins. 

 Glenorchy Reef. 



This outcrops on the steep left bank of the Bucklerburn, a 

 mile and a half above its mouth at Glenorchy. The country 

 rock is a slate, striking north and south, and dipping to the west 

 at from 30° to 50°. The vein strikes east and west, and dips 

 to the north at a mean angle of 15°. It has been followed on 

 the surface for about half a mile, is well defined, with fairly 

 smooth walls, and carries a strong continuous seam of quartz 

 throughout. Its width between walls varies from 1 ft. to 5 ft. 



In accordance with the varying width of the walls, the vein 

 is lenticular in longitudinal section, a feature which evidently 

 indicates some displacement of the walls of the' original fissure 

 (% 1). 



Fig. 1. 



* Sir J. Hoctor, " Outline of New Zealand Geology " (1886), p. 83. 



t Captain F. W. Hutton, " Geology of Otago " Dunedin, 1875), p. 29. 



