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Ngā Tohuwhenua Mai Te Rangi: A New Zealand Archeology in Aerial Photographs
Copper
Copper
Copper was one of the important early ventures in the Nelson mineral belt. Other important copper sources were in Central Otago and Westland. 18 In the north, another important source was Kawau Island. This was the site in 1844 of the first significant mining venture in New Zealand. The mining was initially for manganese, but it was soon found that the associated copper was of more value. Although the source was rich in concentrated copper, there were two major limitations: it was predominantly below sea-level and had to be worked using de-watering technologies developed for working Cornish tin mines, and the copper was bonded with sulphur in a way that required extensive roasting to enable the copper ore to be transported and further refined. The mined ore itself was unsafe to transport any distance because it was subject to spontaneous combustion. 19 Both these technological difficulties required plant which has left striking archaeological evidence: the pumphouse chimney at Miners Point and the smelterhouse in Bon Accord Harbour. The chimney was for the furnace which created steam for the mine's pump, driven by a Cornish beam engine. The chimney survives today more or less intact with part of the wall of the pumping machine building still attached. The pump serviced shafts that went down approximately 60 m below sea level and horizontal workings extending over 200 m. 20
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Early copper mining on Kawau Island, dating from 1844
The smelting house lies behind a fence because of its unstable walls. At the rear of the fence are the excavation squares in which roasting furnace foundations were found under a layer of demolition rubble. The smelting house itself is about 12 by 35 m in plan.
The smelting house, with its walls propped, is currently in unstable and potentially dangerous condition. At its rear towards the foot of the hill, recent archaeological investigations by Rod Clough have shown something of the original roasting furnaces of 1849 which were decommissioned because they performed unsatisfactorily. In the smelter house itself further roasting (to drive off the sulphur) was undertaken and the ore was refined to regulus or matte (impure forms of metallic copper). The Kawau venture was abandoned by 1855, although there were attempts at further mining at the turn of the century. 21
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The Miners Bay pumphouse remains and chimney. The chimney is stabilised by the stone walls of the pumphouse; its upper courses are brick. The pumphouse de-watered shafts extend up to 60 m below sea level. The solid cylindrical object immediately to the left of the wall is probably the sealed head of Whitaker's shaft, the deepest of the shafts. The chimney is about 13 m tall.