Gold Electrum

Gold usually occurs alloyed with some silver; however, when the silver content is between 25 and 55% the mineral is called electrum. Electrum has a pale yellow colour, due to the silver content, and a lower density (13.0 – 16.0) than gold.

A term commonly used to express the purity of gold or concentration of silver is fineness, defined as: (wt% Au) x1000/ (wt% Au + wt% Ag). This formula provides a measure of the relative concentration of gold and silver rather than and absolute gold concentration, and becomes less meaningful with increasing concentration of other metals such as iron and copper. Fineness is most usefully applied to an analysis of bullion. As silver tends to report with gold in most process flowsheets, an indication of ultimate bullion fineness can be estimated from the relative Au and Ag concentrations in an ore or concentrate sample or from microprobe analysis of gold grains.