The application of the cyanide process to the extraction of the precious metals from ores has greatly limited the usefulness of amalgamation, for the reason that no amalgamation process alone thus far devised will save a commercial percentage of the total content of metal in the more refractory ores, while a cyanide process will. The practice, therefore, tends to discard the amalgamation process, unless there is coarse gold in the ore, which can be caught with mercury when ground to a slime, but which will not readily dissolve in cyanide. If we use the cyanide process entirely, we are able to grind faster at less expense for it is not necessary to arrange the intermediate crusher, such as stamps, for both crushing and amalgamating, but for crushing only.

There is a diversity of opinion as to the effect of cyanide of potassium on amalgamated copper plates when crushing in cyanide solution, due no doubt to the diverse character of the ores treated. If the plates are protected by a thick coating of amalgam, cyanide solution may be used with little fear of the plates being corroded, but a greater percentage of gold will be amalgamated without its use. In a cyanide process the loss is more than compensated by the gain in extraction and the simplification of the process due to adding the chemical in the mill water. There are many mills crushing in cyanide solution with nothing extraordinary to note, but some show conditions that are of general interest. A few examples will suffice.

C. J. Stone says in relation to the Free Gold mill that "The amalgamation in the cyanide solution is unsatisfactory, only about 10 per cent, of the total gold being recovered on the plates. The solution hardens the plates and renders them almost of no value for amalgamating after 3 or 4 months' run."