Gold processing Britannica
Thegold was concentrated by washing away the lighter river sands with water,leaving behind the dense gold particles, whichcould then be further concentrated by melting. By 2000 bc the process of purifying gold-silver alloys with salt to remove the silver was developed. The mining of alluvial deposits and, later, lode or vein deposits required crushing prior to gold extraction, and thisconsumed immense amounts of manpower.