Opinion ID: 493685
Heading Depth: 2
Heading Rank: 2

Heading: Sunshine's Antimony Production

Text: 4 Sunshine's ore is valuable chiefly for its silver content, but antimony is recovered as well. Recovery of antimony not only yields a marketable metal, it also facilitates the ultimate smelting of the silver. 5 The following is an outline of Sunshine's operation. The raw ore is first crushed and then separated by a flotation process into high grade silver-copper concentrate, several low grade concentrates, and worthless waste rock. The waste is discarded and the low grade concentrates are sold to smelters which recover lead and iron. The high grade concentrate cannot profitably be sold to a silver smelter until its high antimony content is reduced by leaching in hot sodium sulfide. Once this is done, the purified silver-copper concentrate is washed and sent to the smelter. Finally, the dissolved antimony is recovered from the leachate solution by electrowinning: direct current is passed through the solution, causing metallic antimony to form on the cathode. The remaining solution can be recycled to leach antimony from a fresh load of ore. 6 The parties agree that the extraction, crushing, flotation and leaching stages of this operation count as mining for purposes of the depletion deduction. They differ on the proper characterization of the electrowinning process.