Baker. — Native Copper on Mine-timbers. 337 



consisted of copper- and iron-pyrites, the surface portion 

 being highly coloured with carbonates and oxides of copper. 

 It is enclosed between green foliated slates on the foot-wall 

 side and cherty slate on the hanging- wall. It strikes about 

 north-east, and at the surface dips at about 70°, while lower 

 down it becomes almost vertical. This lode was opened up 

 by a shaft sunk on the foot-wall side, and was worked by a 

 system of levels and stopes. 



Owing to a question of ownership this shaft occupies a 

 unique position, having been started on the beach below high- 

 water mark. In consequence, the collar of the shaft had to 

 be raised out of reach of the tide by means of a double box of 

 planks made watertight by well-puddled clay. The shaft was 

 worked successfully for a number of years, but about forty 

 years ago operations were suspended. At this time the reef 

 was about 15 ft. thick, and averaged 16 per cent, of copper. 

 On this shaft being abandoned the sea very soon found 

 ingress into the mine, and for years past the waves have 

 washed over the mouth of the shaft for several hours every 

 day. 



During the present year it was decided to again open up 

 this mine. The collar of the shaft was again built up, and the 

 workings were drained by means of Cameron pumps. It was 

 then found that large masses of native copper were adhering 

 to the sets of timber in the shaft and to the floor-boards in 

 the levels. These masses were generally found as excres- 

 cences growing from a nucleus, and varied in diameter from 

 ■|in. to nearly 1ft. "When disclosed in the mine it had the 

 peculiar red colour of pure copper, but on exposing it to the 

 air it quickly became tarnished. I examined this copper both 

 microscopically and chemically. Looking at it casually it 

 appears as small imperfect crystals arranged radially from a 

 centre, with numerous beautiful crystals branching from the 

 main stems. Examined under the microscope it is seen to 

 be composed of crystals of the isometric system, in which 

 octahedral faces predominate, though I noticed some good 

 examples of pentagonal dodecahedra. In one peculiar in- 

 stance I found that one branch was composed of twinned 

 octahedra, giving the edge of the branch a very regularly 

 serrated appearance. 



On examining chemically I found that the crystals were 

 pure copper, but were coated on the outside with compounds 

 of manganese and iron. 



I looked for the cause of the tarnishing of these crystals 

 in the presence of these impurities, and found that when the 

 crystals were well washed in water freed from air they were 

 not nearly so liable to become discoloured, but when allowed 

 to dry just as they came from the mine a coating of oxide was 

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