Refining Gold

Refining is the most spectacular part of the process. Silica, borax and soda ash are added to the dried precipitate (or steel wool, in the case of CIP), which is heated in a furnace. This results in a miniature smelting operation. On the top of the melt is the slag containing the impurities, while the molten gold’s greater density causes it to sink to the bottom.

When the furnace’s contents are completely melted, the furnace is tilted and the molten material is poured into a conical mold. Wothless black slag forms on the top and is broken from the underlying gold button once it cools.

The button or buttons (there may be enough precipitate to necessitate more than one melt) are again placed in the furnace, melted and poured into bar molds.

Finally the bars are weighed, small samples are removed to determine purity (expressed as fineness in parts per thousand) and the bars, called doré bars, packed for shipping. In due course, the mine receives a check for the gold.