GRAIN SIZE ANALYSIS AND GEOTECHNICAL PROPERTIES OF MINE WASTE FROM TONOPAH, NEVADA: INITIAL STEPS TOWARD RECYCLING AND REMEDIATION

Tonopah, Nevada is well-recognized for its extensive silver mining in the 1900s that produced approximately 5 million tons of ore and in current day value at least $2 billion in silver. As a result of these operations extensive amounts of mine waste have accumulated in and around the town. These wastes have housing built on them, have a great deal of recreational activity associated with some and are uncovered and are exposed. Little work has been done to characterize these materials until recently with the efforts of our lab. One major issue is understating the grain size and geotechnical properties of these materials in the event that they would be reprocessed for secondary silver or gold recovery or they would be moved and used in some way as recycled media for either construction or a commercial product. Preliminary grain size analysis and field work indicates that there are three types of waste – a white clay rich waste, large boulders, and a highly mixed waste that more variable. Clay rich waste may be suitable for basic ceramic or brick production provided pyrite could be separated. Pyrite may be a carrier of gold content. Highly mixed waste has pyrite and iron oxide minerals and appears to be the most variable with respect to lithologic composition and grain related properties. Larger boulder and clast material may be suitable for geotechnical applications that do not involve extensive water contact. These larger clasts may not be suitable for heap leach based on high quartz content and no major show of Au and crushing required. Both a careful economic analysis and an environmental analysis must be undertaken before efforts of recycling mine waste into either commercial products or geotechnical media proceeds. Critical in these efforts would be the inclusion of local community businesses, government and citizens as extensive recycling of waste would modify the nature and look of the town and have real and perceive economic and environmental impacts.