Abstract

The Bingham mining district was discovered in 1863, shortly after Caucasian civilization reached the Great Basin. For many decades argentiferous galena-sphalerite ores were produced from steeply dipping veins and bedded replacement deposits. Copper occurrences were known, but largely uneconomic. Recognition of the copper-rich mineralized porphyry body at the center of the district had occurred by the end of the 19th century. Breakthroughs in mining technology were required to make the deposit minable, but once begun the mine rapidly became the largest in the northern hemisphere. Large contact metasomatic copper deposits also were developed in limestone units adjacent to the Bingham stock. A number of careful workers, both famous and forgotten, contributed to the general knowledge of base metal deposits at Bingham. A major lawsuit led to careful studies of the replacement deposits by noted experts.Prior to mining, the Bingham porphyry copper deposit was characterized by a leached, iron oxide-rich capping, typically containing several tenths of one percent copper and also traces of gold. Telluride minerals were present locally. Coarse placer gold and boulders of ferruginous conglomerate occurred in adjacent drainages. The larger high-grade veins of the district radiated from or occurred near the boundaries of the mineralized portion of the stock.Deep underground workings followed lead-zinc ores to 5,000 feet vertically beneath the surface and work is now in progress to mine copper ores below the 3,300-foot level of the old underground mines. Open-pit mining has reached depths of 2,500 feet below the original outcrops.The district contains a very barren pluton (Last Chance stock) and a metal zoning pattern that extends only relatively short distances outward into country rock. A few square miles of gravel cover could have effectively concealed the highly economic copper-rich center of the district.

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