When it’s time for you to sell gold (or any precious metal), it’s important to have it evaluated correctly and accurately, by a modern assay laboratory committed to proper evaluation, so that you are compensated honestly.
Assaying is the process by which the purity of a metal is determined. Separating and purifying precious metals from other metals is called refining, while smelting is the separation of precious metal from non-metallic impurities.
Gold dust is the form of gold that is collected by panning for gold or other forms of placer mining, and is composed of flakes and occasionally small nuggets. If you want to sell gold dust, the easiest way to do so is to find a company that can assay (test) and refine the gold. There are several ways to sell gold dust either online or through a local dealer. Whichever method you choose, the steps you need to take are pretty much the same:
First, find out what the current market prices are for gold. Prices for both refined gold (gold bullion and investment coins) and unrefined gold vary with the commodity price of the metal and can change from day to day.
Then have your gold dust tested (assayed). Assaying determines whether your gold dust is real gold and what the purity is. Buyers will want to see an assay report before purchasing your gold dust.
Next, locate a dealer to buy your gold dust. In many cases, assay services also refine precious metals, so you may be able to test and sell gold dust at the same time.
Now, sell your gold dust. You will not get a price per ounce equal to the daily spot price of gold because the buyer must allow for the costs of refining the gold dust. However, good buyers will give you fair prices, especially if you get quotes from multiple buyers.
To assay gold yourself, you will need several materials and more than a basic understanding of chemistry to perform the process to determine the amount of gold in your sample. Prior to performing your own assay, research the process thoroughly, consult professionals and view photos of the process to get perspective on the intensity and outcome of testing.
Laboratories that perform gold assay consider the fire assay method the most preferred technique. It is the oldest known method of assaying gold and continues to be one of the most accurate. When gold is melted, a sample of the gold is taken either by drilling through the poured bar or by capillary tube sampling while the gold is in a molten state. The sample is weighed very precisely and the amount recorded. It is wrapped in assay lead foil along with a quantity of pure silver, then placed in the furnace in a cupel (a special kind of disposable crucible).
All non-precious metals are absorbed by the hot cupel leaving the precious metals behind in the form of a button, which is removed, brushed, hammered flat, rolled thin and then heated in a porcelain crucible containing a weak nitric acid solution. The acid removes the silver, which is poured off and the silver is recovered from solution. The gold is rinsed in distilled water to remove any residual acid, then dried and is now at least 99.999% pure! The sample is weighed again and the original weight of the impure sample is divided into the weight of the now pure sample. The result is the assay. In the analysis of platinum group metals, roughly the same procedure is followed, but the final element readings are normally done using ICP-OES.
ICP-OES (“Inductively coupled plasma optical emissions spectroscopy”) is a major technique for elemental analysis. The sample to be analyzed is normally first dissolved and then mixed with water before being fed into the plasma. Atoms in the plasma emit light (photons) with characteristic wavelengths for each element. This light is recorded by one or more optical spectrometers and when calibrated against standards the technique provides a quantitative analysis of the original sample. ICP instruments are comprised of various optical spectrometers, nebulizers, spray chambers, ICP torch and RF generators.
X-Ray fluorescence (XRF) spectrometry is a non-destructive analytical technique used to identify and determine the concentrations of elements present in solid, powdered and liquid samples. The spectrometer measures the individual component wavelengths of the fluorescent emission produced by a sample when irradiated with X-rays.
Trained assay staff can accurately determine the purity of most precious metals either by electronic means or by basic scratch and touch stone testing with acid, which compare scratch marks from unknown karat gold items with known karat gold needle marks. The touch stone is a smooth fine grained, slightly abrasive black stone, usually quartz or jasper. It was used as the first method of assaying gold, at least as early as 500 BC. Touch stones and karat needles are still used today and can be purchased from jewelry supply houses. They are not anywhere near the accuracy of a fire assay, but still serve as a valuable tool to test the karat value of unknown gold items.
There are numerous electronic testers on the market that will tell the karat value of gold items and some that can test for platinum. Electronic testers are also not as accurate as fire assay, but can serve as a tool to get a basic idea of what an unknown piece of metal is (or isn’t). Electronic gold testers are available through jewelry supply companies.