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The Pamphlet Collection of Sir Robert Stout: Volume 70

(7) Silver

(7) Silver.

As has already been stated, the gold found in the Auckland district is alloyed to a considerable extent with silver, the latter sometimes forming 30 per cent, of the mass, and it is from this source that the bulk of this metal exported from the colony has been derived.

Quite recently a silver-mining field has been opened up at Puhipuhi, about 22 miles from Whangarei and 16 miles from Kawakawa, in the Province of Auckland, The discovery was made by gum-diggers in October, 1888; the field was proclaimed in March, 1890, and was immediately "rushed;" but, as is frequently the case, a reaction seems to have set in, partly, no doubt, on account of the exceedingly bad roads. The reefs are of varying thickness, from 7 feet downwards, and the page 49 ores found comprise argentite or silver glance, pyrargyrite or ruby silver, and small grains of the native metal. Gold is found in small quantities. Mr. Alex. McKay, F.G.S., has recently visited the Puhipuhi district, and according to the Colonial papers of Jane 9th, 1892, considers that the field forms part of a mineralized district extending along the eastern coast of Auckland peninsula both north and south. The reefs, he states, are well defined, and prove that they live to a vertical distance of 500 to 700 feet. Almost all the leads contain silver ore, though at present the average yield is not sufficient to enable it to be treated profitably; but Mr. McKay's opinion is that the district is a legitimate field for mining enterprise.

A number of assays made from a lease known as the Prospectors' Ground gave from 200 ounces to 10 ounces per ton, and specimens from No. 8 reef as high as 2,000 ounces, while the average of nine assays was 128 ounces. The plant on the ground consisted in 1890 of a stonebreaker, one pair of Cornish rolls, a pulverizer, four amalgamating-pans, etc.

From the time the field was open, to the commencement of 1891, twenty claims had been taken up, and a small amount of work done; but, so far as the writer is aware, the bulk of the operations seem to have been purely of a prospecting nature.

A remarkably interesting and apparently valuable deposit of silver ore occurs near Collingwood (Nelson), on the Parapara River. The lode was discovered by Mr. Washbourne, and the character of the stone was determined in the Colonial Laboratory, where it had been sent for analysis as an iron ore. The containing rock is gneissic schist, passing into steatite, and farther to the west are slates and fine ciystalline marble; the lode when first discovered was about 24 inches wide, and yielded from 21 ounces to 1,792 ounces of silver per ton. It subsequently increased to 5 feet in width, but the yield went down to from 22 ounces to 51 ounces per ton. At the bottom of the shaft a return of 85 ounces to 110 ounces was obtained.

The lode was sunk on for 56 feet, and driven on for 36 feet, and from the end of this drive, where the ore had changed to an argentiferous galena, 5 tons was got, which averaged 40 ounces of silver to the ton, and 3 cwts. yielding at the rate of 300 ounces. The lode in this part then became barren, and work was stopped for fear of letting in the water from the river. Other works were then carried out, which succeeded in proving that the lode was well-defined, extended over a considerable area, and was of variable thickness and richness. The ore, which has been named Richmondite, from the locality where it occurs, is a variety of tetrahedrite, and gave the following percentage composition:— page 50
Per Cent.
Sulphide of lead 36.12
Sulphide antimony 22.20
Sulphide bismuth traces.
Sulphide copper 19.31
Sulphide iron 13.59
Sulphide zinc 5.87
Sulphide silver 2.39
Sulphide manganese .52

The mine has not been worked for some years.

In 1889, geocronite or antimonide and sulphide of lead, yielding 125 ounces of silver to the ton, was brought from Collingwood. Another deposit of silver ore, occurring at Mount Rangitoto, 20 miles south of Hokitika, merits a passing notice, On the southern face of this mountain is a lode 10 inches thick, consisting of pyrites, with about 20 per cent, of galena. A specimen brought by Mr. Cox assayed 10 ounces 17 dwts. of silver per ton; but samples tried in the Melbourne University Laboratory gave a yield of 735 ounces. The highest obtained by Mr. Skey, the able chemist attached to the New Zealand Colonial Laboratory, was 10 ounces 17 dwts.; but it must be remembered that the Melbourne University results were given on the galena, and not on the ore.

As the workings were continued the lode changed to a vein of solid pyrites, with a very little galena scattered through it.

During 1890, the amount of silver exported was 32,637 ounces, valued at £6,162, whereas in 1871 it was 80,272 ounces, valued at £23,145. Altogether since the commencement in 1869, 554,610 ounces, valued at £134,997, have been exported.