Gold concentrates: The options for treating gold concentrates are in direct relation with its gold contain, thus gravimetric concentrates have been treated by amalgamation following by retorting of the amalgam and smelting of the product. This is usually still the most efficient option, but considering the health hazard of mercury, several alternatives must be considered.
High grade concentrates, typically more than 300-500 g/t can be directly smelted, provided that the material does not contain minerals that could adversely affect smelting, e.g. sulphides.
Sometimes flotation can be used to upgrade concentrates for direct smelting, but this is rarely applied. The effectiveness of the process depends on the nature of the material and the degree of gold liberation.
Smelting is an option for treating gold flotation concentrates, however the lowest grade that can be considered for smelting is more than 300 g/t, depending on the content of other metal values (copper, silver, platinum group metals), the concentrations of penalty elements and shipping distance