Silver production from the Silver King Vein, Calico, California: A forensic geology estimate

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The Calico District is regarded as a historically important contributor of silver in California, with 13-20 million troy ounces of silver officially reported mined. However, these reported values for the entire district are inconsistent with reported ore grades and volumes mined from the King Vein alone. Underground mine mapping with laser range-finders was conducted under supervision of the mine rescue squad and county search and rescue to produce accurate stope maps along the King Vein. Silver ore grade maps for these stopes were made from fire-assay and portable XRF analysis of ore remnants in pillars and stope borders. It is assumed that remnant ore represents a minimum ore grade, not a maximum. The resulting volume and grade estimates provide a more accurate picture of the minimum amount of silver removed from the King Vein. This research suggests that at least 26 million troy ounces of silver were produced from this single vein alone. Assuming a 20% milling loss, this still indicates that the King Vein yielded at least 21 million troy ounces of silver. This estimated production of the King Vein exceeds the high-end historical estimate for the whole district, even without contributions from the Red Jacket, Oriental, and Bismarck veins. This suggests that, at best, the privatelyheld companies at Calico kept poor records. But given the remote location of this early district, the proximity to Mexico, and elevated black-market silver prices, it may indicate an intentional and systematic effort by these companies to defraud the government of tax revenue.