The smelting of copper (Cu) results in the atmospheric deposition of Cu onto surrounding soils.  Excess concentrations of Cu in soils can be absorbed by plants to phytotoxic levels or leached into the groundwater, threatening the entire ecosystem.  A means to limit the bioavailability and mobility of Cu is to remove it from the aqueous phase by applying an adsorptive material.  A synthetic clay (highly charged swelling mica) was tested for its ability to decrease the concentration of free and exchangeable Cu in 15 Chilean soils near 3 different Cu mining operations.  The studied soils contained 112 to 2790 mg Cu kg^-1 soil, which were excessive levels when compared to typical values (13 to 24 mg Cu kg^-1 soil).  Exchangeable Cu ranged from 0.3 to 22.9 mg Cu L^-1, and was generally higher than the maximum contamination level goal (MCLG) for Cu in drinking water set by the EPA (1.3 mg Cu L^-1).  The synthetic clay was applied to each soil at rates of 0.1%, 1%, and 2% by mass.  A 2% sodium-montmorillonite treatment and the non-amended soil served as controls.  Each sample was brought to field capacity once per week, and the soil pH, free Cu²⁺, and exchangeable Cu were measured periodically for 4 months.  The order of the efficacy of the treatments in reducing exchangeable Cu and free Cu²⁺ for soils with levels above the EPA's MCLG was: 2% mica > 1% mica > 2% montmorillonite > 0.1% mica.  At 4 months of incubation, the 2% mica treatment reduced the exchangeable Cu concentration below the EPA's MCLG or slightly above (< 2.4 mg Cu L^-1) for all soils.  This synthetic clay has promise for the remediation of small trace metal-contaminated areas, such as Brownfield sites.