A distinctive feature of mining in the Duller district was the discovery in 1865 of the ‘beach leads’ of gold. They were layers of heavy sand containing a considerable quantity of gold formed by the action of the waves, tending always to sweep back the lighter material cast up and to leave behind the heavier. In the course of time, as the sea-coast was built up, later deposits of light material covered some of the leads, and in order to trace out the line of richest deposit, miners had often to construct tunnels extending many hundreds of feet into the hills.

Apart from gold extracted and laid down by water, there was gold still embedded in quartz, forming ‘ reefs.’ Quartz-mining was a company affair, requiring considerable outlay before any return could be expected. The quartz-mining area of New Zealand was the Hauraki goldfield in the Auckland Province. Small reefs have been found in the Otago and West Coast areas, but not con­taining gold in extraordinary quantities. In quartz-mining, the gold-bearing rock was crushed by ‘ stumpers’ or ‘ rollers,’ and the gold extracted by chemical means—in the early days by passing the crushed ore over mercury, which formed an amalgam with the gold, and more recently by the more efficient cyanide process.

Reef mining and prospecting for reefs require a considerable technical knowledge of geology and metallurgy, and in order to assist miners to acquire this knowledge, in 1885 Schools of Mines were set up on the various goldfields. The interest and satisfactory progress of the miners fully justified the efforts made on their behalf by Professor Black and his able band of assistants, and warranted the help given by the Government in the purchase of materials for demonstrations.