MINERAL SANDS OF NEW ZEALAND.

Evening Star, Volume VII, Issue 2003, 6 October 1869, Page 3

MINERAL SANDS OF NEW ZEALAND.

Dr Hector Ins delivered at Wellington another lecture on “Mining in New Zealand.” In the course of his lecture, he referred to the mineral sands of the Colony, and the clue to their sources aflorded by the composition and size of the particies. As might be expected, alluvial gold is found to vary in composition according to the nature of the rock which formed the original matrix; thus in Otago the gold is pure, or only alloyed with a little copper; at Wakamarina, silver appears in the propoi’tion of seven per cent, whilst on the other side of the Strait it contains double that proportion; and in the North, at Auckland, it forms 35 to 40 per cent, of the weight of the gold. In the South, the gold is associated on the other hand with platina, zircons, and garnets ; and in the Nelson Province, with the rare mineral, osmiridium. In like manner, the black sands vary in composition for the same reason. In the neighborhood of the basaltic rocks, as at Dunedin, it contained 75 per cent, of titanite of iron, which is a refractory compound of the oxides of titanium and iron, while in some parts of the interior of Otago, the sands consist either of magnetite of loadstone, or of haematite, both of which are pure oxides of iron, and more valuable as ores. On the West Coast the sand has the latter character, and it is worthy of remark, that notwithstanding its proximity to volcanic rocks, Taranaki sand, from its composition containing only 8 per cent, of titanic iron, belongs to the sands derived from the older rocks, principally syenites and altered greenstone slates. The distribution of these sands, according to the size of their particles, is very instructive, the deposits being of two kinds—beachformed and river-formed. The former are principally on the West Coast, both gold and iron sand being of very fine grain. The greatest altitude at which any beach gold has been found is about 125 feet above the sea, at Watchman’s Terrace, north of the Grey River. It is found everywhere from Cape Farewell to Jackson’s Bay, the richest deposit being at Okarito, about the centre of the great Westland bight. The coast line south of this does not favor the fine gold, having bold rocky shores and headlands. On the sandy beaches of the south and east coast it again appears, and has been found as far north as the commencement of the shingle formation of the Canterbury plains. In the North Island the sand deposits have their maximum at Taranaki, but extend north and south of that place, never being found at a greater height than 90 to 100 feet above the present sea level. No gold has yet been found with any of these deposits in the North Island.