Gold Dust, Dore Bars and Jewelry – Assay and Refining
Gold Dust refers to fine particles of elemental gold found in riverbeds, stream beds, and floodplains. Alluvial deposits are either dredged from pond and river bottoms or sluiced from banks and floodplains with high-pressure hydraulic hoses.
Dore Bars are typically created at the site of the mine by melting and pouring unrefined low grade gold into a graphite bar mold. Dore bars sometimes weigh as much as 25 kg, twice the size of a standard London Good Delivery bar.
Gold Jewelry, or scrap jewelry, is based upon a karat grading process. Gold in its purest state is referred to as 24-karat gold. Pure 24k gold is normally too soft for use in jewelry, so jewelers mix gold with another metal like nickel or silver to harden it. Karat Gold is a gold alloy of not less than 10 karat fineness, up to 22 karat fineness.
We buy all forms of gold.
Assaying is the process of testing gold or silver to determine its fineness or purity. Before gold is refined, it must either be weighed or the client and the gold refiners must come to terms with an agreed estimated metal to gold content before the extraction is done. This ensures that the client will get a fair price for the gold and is aware of its total cost. In the case of dore bars, or jewelry, the assayers will then take a drilled sample of the gold and will have it tested in a lab to determine the gold content. Gold is also stamped on a bar or a piece of precious metal to guarantee its fineness. Assay marks and karat stamps are solid hallmarks that help calculate gold amount and pricing.
The process of refining gold is quite complex. It requires not just equipped gold refineries, but highly experienced gold refiners to carry out the potentially dangerous task of refining gold. Gold refining services employ various methods to recover metal and to refine scrap gold for its reuse.
Gold refining begins with amalgamation or cyanidation.
Amalgamation is the process of combining gold ore with mercury by either slurry mixing techniques or grinding. The resulting amalgam is heated to distill off the mercury.
Cyanidation is a process of oxidizing gold and dissolving it in an alkaline cyanide solution, based on the Elsner reaction, to allow the gold-bearing solution to be separated from the solids. This is accomplished for higher grade ores in large tanks (vat leaching) or for low-grade ores, by spraying a dilute cyanide solution over the ore (heap leaching).
We hope this helps you better understand the challenges of refining gold.