How did mercury form an amalgam with silver in the patio process?

In the patio process, mercury formed an amalgam with silver through a chemical reaction facilitated by the addition of salt and copper sulfate to the crushed ore.12

After the ore was ground into a fine mud in an arrastra and spread across a courtyard, or patio, these reagents were mixed into the mass by driving mules over it. This mechanical mixing ensured the reagents were thoroughly incorporated, triggering chemical reactions that freed the silver from its compounds. Once liberated, the silver dissolved into the mercury, as elemental silver is naturally soluble in mercury when brought into contact with its surface.123

This process effectively wetted and dissolved the silver particles to form the amalgam. Following the reaction, the mixture was washed to remove the mud, leaving the denser amalgam at the bottom to be collected and heated to recover the silver.31