Dillon Gage Refinery provides the most accurate assaying services in the industry. An assay is a critical part of refining. Though this process, we carefully analyze the metal composition of your lot. In order to determine the purity and composition of your scrap lots, it will be melted and then sampled. Each sample is clearly identified as to customer and lot number. With this sample, we are able to determine the content of the metal via a fire assay or the use of X-ray fluorescence (XRF).
Fire Assay, also known as cupellation, is an age-old process and is the industry standard for precious metals. This process analyses a sample from a homogeneous melt of the lot. The sample along with silver is wrapped in lead foil and placed in a porous bone-ash cupel and melted. The lead foil pulls the base metals into the cupel leaving a gold and silver dore bead. After treating the dore bead with nitric acid to remove the silver, the remaining precipitate is dried and weighed to obtain the concentration of the precious metal. This is a time-consuming process and typically takes about 5 hours to complete.
XRF/ X-Ray Fluorescence Spectroscopy
X-Ray Spectroscopy uses the phenomenon of fluorescence to determine the concentration of elements in a sample. Fluorescence is the phenomenon in which the absorption of a specific wavelength of energy (X-Rays) by a material results in a re-emission of radiation of a lower energy. This difference in energy is measurable and is characteristic of the atoms present in the material. The primary advantages of this method are that it is non-destructive and is very fast.
When is one process used over the other? Typically, larger lots (AU>50 ozs. AG>500 ozs.) use fire assay process. Should you request one over the other? Both forms are very accurate and are within .10% of each other but the fire assay adds at least 1 more day to complete lot.
Our refinery takes this step very seriously because we take the trust of our clients, and the entire precious metals industry, very seriously. In fact, major jewelry vendors rely on Dillon Gage assayers to verify the purity of their inventory.