Although a relatively obscure metal, thallium is found in many mining waters and, because of its toxic nature, must be removed to low levels. A low cost natural zeolite, clinoptilolite, has been found to effectively remove thallium from water at a closed gold mine. Thallium is a soft metal now used in electronics, pharmaceuticals and glass manufacturing. Due to its potential toxicity, it is the primary contaminant of concern at the Kendall Mine in Montana.