Most prospecting and mining in New Zealand has been undertaken privately, although the Government has always given direct and indirect assistance. At the height of the gold rushes of the sixties the basis of mining was the one-man claim of 100 ft by 100 ft. But amalgamations of up to 100 acres for special (“extended”) quartz claims, and increases to 2,000 acres for dredge claims, allowed the entry of companies with larger capital resources so that by 1910 a score of companies had paid-up capital exceeding £10,000. By the time of the depression of the 1930s, when small-scale mining recommenced temporarily, three of the few companies left – Waihi, Blackwater, and Rimu (dredging) – each had subscribed capital in excess of £200,000.

The scale of coal mining operations has also increased, although the inheritance of British mining traditions led to the early formation of some large companies. In 1963, when Kopuku Opencast was by far the largest producer and supplied much of its output of 470,383 tons to Meremere Power Station, 16 mines produced over 50,000 tons of coal each, and 13 employed over 100 men. The average figures per mine were 19,500 tons and 25 men for each of 141 mines, with by far the greater number of small mines in the South Island. Comparable figures for 1890 were 4,000 tons and 12 men for 153 mines.

The State entered coal mining with the State Coal-mines Act of 1901, but the greatest expansion of its activities was during and after the Second World War when many private mines were purchased. Kopuku apart, the State mines, which are directly controlled by the Mines Department, produced 65 per cent of all coal in 1963. Most other mining is carried on by parties of a few miners, or by individual owners employing a very small staff of less than a dozen. The only exception, with assured coal reserves, is Glen Afton Collieries Ltd. which not only operates the Glen Afton and MacDonald mines in the Waikato with a combined 1963 output of 253,120 tons, but also has a joint interest with the State in Kopuku Opencast.

Apart from the operations of the State in the Glenorchy scheelite mines during the Second World War, and the interest of certain Government Departments in quarrying (e.g., railway ballast pits, forestry road-metal quarries), all quarrying and metal mining is conducted privately by concerns ranging from one-man part-time operators to major companies working a chain of quarries. Many of the latter combine quarrying with other operations such as transport, cement making, and brick and concrete-block manufacture. On the average three men were employed in each quarry in 1963 for an average quarry output of about 17,500 tons.