In the 1880s the gold mining industry encountered severe problems in the extraction of gold from unoxidised ores which were being met more frequently. The gold extraction technology of mercury amalgamation became more inefficient to the extent that little more than half the assayed gold content of the ore was being extracted. Clearly, a major breakthrough in metallurgy was required to overcome this problem. This occurred through the development of the cyanide process which not only raised the percentage of gold extracted from unoxidised ores but also, because of its cheapness, allowed much lower grade ores to be mined and treated than had been possible previously.