Samples accepted for assay from gold and silver refinery section include mine bullion, Dore bullion delivered to the silver refinery from the by-products recovery section, gold anodes, gold cathode deposits, electrolytic gold, gold alloys, fine silver, control process samples, research samples, and other minor samples. Samples from the By-Product recovery area include incoming materials, lead bullion, matte, speiss, slags and process control samples. Routine gold and silver assaying must be made on twin stream duplicate system. In order to ensure the independence of the two bullion streams, the assay lab must be divided into two separate assay offices. Each has its own staff, balance room, proof gold, and entirely separate set of equipment.
The main advantage of twin-stream procedure is based on its ability to reveal possible assay bias, which could not otherwise be detected. Although a duplication of work and equipment is involved, the system is not more expensive to operate. Operations run in both streams so that assays are completed more rapidly and at less cost than would be possible under a single stream unit using a comparable number of replicates and the same degree of proof control. Basically, the independence of the two labs is maintained throughout the entire assay process. The streams only converge when the completed assays are compared prior to reporting.
Several tons of material is received for treatment, containing variable gold and silver contents. Borax slags from mine smelting operations, followed by miscellaneous concentrates, calcines, ashes, sweep from the gold and silver refineries, other sweepings, brick pots and liners, precipitator sweeps from the gold and silver refineries, base bullion bars and jewelers sweeps. Material delivered for treatment is required to be 100% passing 10 mesh (1.7 mm). Some exceptions are base bars and other metallic lots, are some borax slags that could be received in lump form.