The Hermosa deposit was discovered in 1879. Production from this and neighbouring workings was carried out between 1896 and 1964 and amounted to about 32,000 tonnes with an average grade of about 250 grams per tonne of silver.
Asarco operated the nearby Trench mine between 1939 and 1964. The Hermosa property was first used as a source of water for the Trench mill, and then explored by Asarco by surface geological mapping and intermittent drill programs from 1964 until about 1980. In total, 104 percussion and core holes were drilled, with an aggregate length of 13,088 metres. A mineral inventory calculated by Asarco in 1984 estimated a resource of 8.7 million tonnes with an average grade of 215 grams per tonne silver. Cutoff was inferred to be 47 grams per tonne silver.*
Arizona Minerals, which is 100% owned by Arizona Mining, acquired the property from Asarco in 2006.
*These historical figures were defined in a report published by ASARCO in 1984, and were later discussed in a Technical Report published by Wardrop Engineering Inc. dated May 6, 2005. Arizona Mining has not done the work necessary to verify the classification of the resource and is not treating the resource figure as a NI 43-101 defined resource verified by a qualified person at this time, and therefore should not be relied upon by investors.