The La Trinidad mine is located 45 km southeast of Rosario, in Sinaloa state, Mexico. This gold deposit was identified and acquired by Almaden Resources in 1992 and an option agreement was signed with Eldorado Resources Corporation shortly thereafter, whereby the Company was carried into production for 49%. A reserve was developed and construction of a heap leach mine commenced in February 1996 with production starting in late 1996.

In April 1998 Almaden disposed of its 49% working interest in La Trinidad to Eldorado for 100,000 shares of Eldorado stock plus a sliding scale net smelter return royalty of 1½% to 2½% depending on gold prices and a bonus of $2.00 per ounce for 49% of any new gold found. Because of low gold prices the mine closed in the fall of 1998.