Stamp Milling

Stamp Milling. . , Gravity stamp milling was the primary method for crushing ore prior to 1910. The purpose of the mill was to reduce gold-bearing rock (ore) into a high-value concentrate of gold. Mills generally consisted of several components: a stamp battery, amalgam plates and a concentrator table., Steam or electric power entered the mill system through a large belt-driven bull wheel set near the top of the battery frame. As the bull wheel turned, cams lifted the tappets attached to each stamp stem. When the cam released the tappet, the stamp dropped onto the ore within a large mortar box. Ore chunks entered the mortar box through a back slot. The stamps pounded the ore to a pulp. Water introduced into the mortar box turned the pulp into a slurry. The slurry passed through a screen and then onto a sloping table attached to the battery below the mortar., An amalgamation process occurred on the inclined table. Copper plates affixed to the table were coated with liquid mercury. Fine gold passing over the plates adhered to the mercury creating an "amalgam." The mercury-gold amalgam was collected and melted in a retort, where the mercury rendered off leaving behind liquid gold., Specks of gold that escaped the amalgam table were introduced to a concentrator table. The mechanical table rocked and vibrated, washing away lighter waste rock. Gold, having a heavier specific gravity, accumulated along ridges spaced across the table top. After the mill run, the "concentrates" were collected and bagged., What you see on display is the original Citizen's mill battery reconstructed inside a new wood frame. The amalgam table is missing. The circular concentrator table worked like a huge mechanical gold pan.