190 



The veins are all of the jDegmatite class, and no doubt 

 have their origin in some intrusive mass below. The most 

 western reef is somewhat different from the others, being 

 chiefly composed of micaceous haematite and quartz, with occa- 

 sional copper stains, and no radio-active minerals have so far 

 been detected in the outcrop. The main reef is about 60 

 yards further east, and has been opened to a depth of 15 

 feet. The vein matter is distributed in a roughly symmetrical 

 arrangement. A massive mineral (1) with an uneven iron- 

 black fracture and specific gravity, about 6. composes laminat- 

 ed zones some four inches wide next the walls. On analysis 

 this proved to be chiefly composed of iron and titanium, 

 though, as evidenced in the thin slice prepared for microsco- 

 pic examinations, it is not homogeneous. The central portion 

 of the reef is occupied by a more compact body of a brighter 

 black mineral (2), with slightly less specific gravity; also ac- 

 companied by quartz and a varying Cjuantit}^ of black mica. 

 Occasionally streaks, scattered grains, and cuboid crystals of 

 a rarer black mineral (3), with specific gravity in the vicinity 

 of 4, are observable, which, on account of its very brilliant 

 lustre and glassy fracture, is readilv distinguishable. These 

 latter two minerals have been shown by Professor Rennie 

 and Dr. Cooke to contain over 50 per cent, of titania, a large 

 quantity of iron, and a notable amount of rare earths, 

 uranium, vanadium, and chromium. 



So far as can be judged at present, the brilliancy of lustre 

 indicates increased percentage of titania chiefly, and to some 

 extent rare earths. Several degrees of brilliance are shown 

 by primary heavy black minerals of the general type of (2), 

 and it is inferred that analysis will reveal a considerable diver- 

 sity in chemical composition. The mineral (1) is likely to be 

 to some extent an alteration of (2), the heterogfeneity exhibited 

 by it aiding in this conclusion. Type (3) is best developed 

 in the main vein, at the contact with the siliceous central 

 filling, and has all the appearance of having formed at a period 

 after the reception of the main bulk of the ore body. In such 

 situations it is also frequently met with crystallized, embedded 

 in the quartz, or presenting idiomorphic faces in its direc- 

 tion. The quartzose gangue in the central portions of this 

 lode contrasts noticeably with the titanium-rich iron minerals 

 and micas forming the general filling, and indicates, at 

 least an alteration in character of the contributing circu- 

 lation. The inception of the new chemical and physical 

 conditions accompanying this change in circulation has been 

 to partially alter the mineral (2) near the contact, leaving 

 two additional minerals in its place, one resembling micaceous 

 iron (4), the other a dull brownish-black ferriferous mineral 



