PawnMaster Blog

Guest blog: The Ins and Outs of the Diamond Recovery Process

Posted on 12 Apr 2019

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The process of diamond and gemstone recovery from karat gold jewelry scrap is far more complex and time consuming than a direct melt and assay recovery. Jewelry that contains recoverable diamond and gemstone melee will always yield a much higher value, as long as the refiner you choose is implementing sound wet chemistry processes that minimizes the potential for mechanical losses of metal and damage to the your valuable gemstones. You should expect the refiner to charge higher processing or treatment fees for this service as well as allowing a little more time for final results but in the end, the additional value you'll receive back from the sale of your stones more than justifies any inconvenience.

The process we use at Mid-States involves a pre-treatment of the jewelry scrap in a heated reaction of dilute nitric acid. This initial digestion attacks the outer surface of the metallic alloy, reducing base metal and excessive silver, while creating more porosity in the metal for secondary dissolution. The pre-digestion also minimizes the amount of silver chloride that can coat the metal surface of the jewelry, which impedes the efficiency of the secondary reaction.

The secondary digestion in Aqua Regia (mixed nitric and hydrochloric acids) is where the jewelry alloy becomes fully soluble into solution, thereby releasing all the diamonds and/or gemstones for later filtration and allowing for easy undamaged recovery. To effectively precipitate the gold, now in solution, we continue boiling the Aqua Regia while continuously adding additional hydrochloric acid to the reaction. Until we drive off all the nitric acid contained in the reaction it is not possible to effectively precipitate 100% of the gold now soluble in the gold chloride solution.

Once the reaction is complete the solution is filtered, stones are recovered and the process of precipitating the fine gold begins. To precipitate the gold, we inject sulfur dioxide gas into the chloride solution. During this process, the gold converts to high purity fine gold sponge and accumulates at the bottom of the recovery vessel, then followed with additional filtration to recover those fine gold solids. The solution is tested to verify the completeness of the reaction until no residual gold remains. The spent acid solution is now further treated and neutralized for proper disposal.

The final stage of the process focuses our attention on your stones and final melting. Our lab technicians will perform the tedious task of hand sorting all diamonds and colored gemstones, removing small particles of undissolved metal and other debris. All removed particulate is added back to the fine gold sponge and forwarded on for final melting and assaying. The stones are put through a final cleaning and if requested by the customer, acid etched to frost the outer surface of CZ's for easier final sorting.

Mid-State does not purchase diamonds and gemstones, as this in an area that I've always felt is a conflict of interest. There are several independent diamond buyers that are well known among the pawn community who are highly reputable and should be consulted for this service. We are fortunate enough to share an office with one of those dealers, Jay Kantor from Jay Pays who is able to provide a free assessment and offer on your stones. This also saves you additional shipping fees for returning your stones.

There are no short cuts to the process I've described above as it is very labor intensive involving multiple steps. There are costs and dangers working with these acids, controlling and treating fumes as well as long-term environmental responsibility that cannot be avoided. There are refiners we compete against that will offer you this service at bargain basement prices as low as $100 or less. Please accept my frank suggestion that it cannot be properly done at those rates. Please contact myself or any of our sales associates for more information on our diamond recovery service and terms.

Jack Brown

Written by Jack Brown

Jack Brown is co-owner and Operations Manager for Mid-States Recycling, Inc., located in Des Plaines, Illinois. Mid-States, a family owned business began operations in 1981 under the direction of Jack’s father Ellis Brown, former President of the Simmons Refining Company of Chicago. Jack, having a background and firm understanding in technical sales joined Mid-States in 1982. Over the course of the next 35 years Jacks’ responsibilities have grown to include all Plant, Laboratory, Gemstone Recovery, Refining, Purchasing and Marketing functions of the company. Mid-States Recycling & Refining is known Nationally as a leader in Precious Metal Refining for the Jewelry and Pawnbroker industries and professions. Jack currently serves as an officer and on committees for the International Precious Metal Institute and a former member of the NPA Board of Directors.

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