This report evaluates the leaching of oxoanions and other materials from mineral processing wastes, using the TCLP test as well as several other alternative leaching tests (Generalized Acid Neutralization Capacity (GANC), Constant pH 5.0 Leaching Test, Constant pH Leaching Test at Various pHs, and Variable Mass Leaching Test). Three actual mineral processing wastes were selected for evaluation. These wastes came from (1) fluvial tailings from the Arkansas River, three miles from the mining district in Leadville, CO, (2) the Anaconda copper mine in Yerington, NV, and (3) from a slag pile at a lead and zinc smelter near the village of Dearing, Montgomery County, in southeastern Kansas. We found that mineral processing wastes vary widely in composition and characteristics. The three samples tested were soil-like and varied in characteristics, with one being classified as a loamy sand, one a sandy loam, and the third a silty sand. Unfortunately, since this study focused on leaching of oxoanions, none of the samples contained significant quantities of these materials. The Yerington, NV sample was the highest, with 209 mg/kg As and 156 mg/kg Se. All three samples had TCLP leachate concentrations well below the allowable limits, except for cadmium in the Dearing waste.