The exploitation of New Zealand's mineral resources began in the sixties with the gold rushes which stimulated development by profitable gold exports. With the exhaustion of these early fields, mineral production fell away. It certainly lacked variety as far as large-scale mining was concerned, but the commonly accepted belief that the country was virtually devoid of economic minerals was far from the truth. Admittedly the production of industrial (i.e., non-metallic) minerals, mineral fuels, geothermal steam, and ground water has increased markedly in recent years while that of metallic ores has dropped. But within the last few years prospecting for iron, aluminium, and uranium has been very active, even when compared with the considerable prospecting demands of industrial minerals – coal, oil, and steam.