The El Castillo Mine, which was formerly called El Cairo, was a grass roots discovery that resulted from a regional exploration program initiated by Battle Mountain Gold while exploring for bulk tonnage, disseminated gold deposits.
Battle Mountain Gold completed 207 RC drill-holes and six diamond core holes (drilled as twins to six of the RC holes) within the El Castillo Mine area. Battle Mountain Gold completed a resource estimate, scoping study, preliminary mine plan and reserve estimate that indicated the potential for a viable mining operation.
Morgain Minerals Inc. took over the project. Its exploration work included completion of six twin diamond drill holes, and 136 RC drill holes.
Castle Gold Corporation, as successor to Morgain Minerals Inc., began its work and changed the project name from "El Cairo" to "El Castillo" in reference to a nearby rock monument of the same name. Castle Gold's work included additional sampling and completion of 21 shallow, close-spaced air-track drill holes in the mining area to up-grade near surface gold resources.
Castle Gold Corporation's work combined with previous work by Morgain Minerals Inc. and Battle Mountain Gold were the basis for a preliminary reserve estimate by A.C.A. Howe International Limited dated January 31, 2008.
The El Castillo Mine sold its first gold in September 2007 from heap leaching begun the previous July. The El Castillo Mine completed the commissioning of commercial production in July 2008 as an open pit/heap leaching operation.
Acquired by Argonaut Gold in December 2009.
Produced an estimated 566,711 ounces of gold as of January 1, 2018. Of this production, Argonaut has produced 520,923 ounces of gold since taking ownership of the El Castillo Mine in 2009.