Low-Grade Refining

Noble goes above industry standards with low-grade bench materials from jewelers and jewelry manufacturers. Noble goes through several steps to make sure all material is captured and refined.

1st Step - Thermal Oxidation

At our facility, Noble uses a custom “burn-out” oven to incinerate all organic, non-precious material leaving behind a semi-fine ash and other solids.

2nd Step - Ball Mill

Once the material has been incinerated, the material is ball milled into a fine, crushed powder.

3rd Step - Sifting

The fine powder is then sifted using 7 different mesh sizes to ensure all oversize is captured. The metallics left over in the prepared sweeps are screened out and the magnetic oversize is removed during the sifting process.

4th Step - Oversize

The non-ferrous metallics are smelted into a cone with a pin-core (sample) taken for fire-assay.

5th Step - Analysis

A sample of the prepared sweeps is taken and assayed to determine purity. This is not our final step, but this is where most refiners stop!

6th Step - Chemical Process

At Noble Metal Refining’s state-of-the-art laboratory, we chemically process the prepared sweeps using nitric acid and Aqua Regia to make 99.99% (.9999) pure Gold, Silver, Platinum and Palladium. The Gold is recovered first by adding sodium metabisulfite to precipitate the Gold. The liquid is then tested with stannous chloride to ensure all Gold has been captured during the chemical process. Depending on the color of the liquid silver, platinum and palladium will be chemically treated to ensure all precious metals have been recovered. These steps will produce the highest accountability for our clients. Because of the complex formulas and chemistry required to produce the highest results, we invite our clients to take a tour of our laboratory and actually see our capabilities. At Noble, we want all our clients to completely understand what we will do with their material.