Stamp Mill

A stamp mill was a mechanical crusher, noisy, heavy and somewhat awkward to operate. The stamps were heavy metal weights that were lifted and dropped on the ore by a crankshaft. The crushed ore would then be further refined, usually by a mercury or cyanide process.

The process explained:

The miner would bring the ore to the mill and load it into the ore car. The heavy ore car would be brought up to the mill on a tram-track by the aid of a winch.

Once the ore was at the top of the mill, the car would be emptied on to a screen called a 'grizzly.' The 'grizzly' was a metal grate with separators about 2 inches apart (about the distance of the claws on the paw of a grizzly bear). Smaller material would fall through the screen and into the ore chute while larger material would slide across the 'grizzly' into the crusher. The larger pieces of ore passing into the crusher would remain until they were pounded into a workable size (less than 2 inches) then fall into the ore chute.

The ore, now about the size of a course gravel would, slide on to the heavy metal plates under the stamp battery where water would be poured on. The battery usually consisted of sets of 5 stamps (5 stamp, 10 stamp, 20 stamp mills, etc). The stamps would be lifted in sequence by a powered cam and then dropped using gravity to to pulverize the ore into a fine, sandy slurry.

The slurry would be spread evenly over the recovery table. The recovery table was a copper-sheeted table that was coated with mercury previous to the processing run. The gold in the sand would adhere to the mercury while the sand would pass over to the next step in the process, the concentration table.

The concentration table was a table with runners which would shake or vibrate, slowing the heavier material containing the gold to a stop while letting the worthless tailings pass to a conveyor to be transported away. The crushed sand from the table would be loaded back into the stamp mill, pulverized further and once again slurried across the mercury coated recovery table.

Once the mercury on the recovery table was full, or the ore run was complete, the gold and mercury would be scrapped off the table and separated. Separation would be accomplished by straining the amalgam mixture through a chamois. Further separation could be done by a retort process. The retort would heat the mercury removing it from the gold as vapor and condensing it for later use. The remaining gold was now in amalgam form, ready for further refinement processes such as smelting into bullion.

Also see:
The Lost Horse Mine
The next year he found a steam-powered, ten-stamp mill somewhere near the Colorado River and had it dismantled and hauled to the mine site. ...

Keane Wonder Mine - Death Valley National Park
In 1906, L.L. Patrick got the bond for the mine, and he announced plans to erect a 20 stamp mill at the foot of the Funeral Range. When his bond expired, ...

Bodie, CA
Gold bullion from the town's nine stamp mills was shipped to Carson City, Nevada accompanied by armed guards. Once the bullion reached Carson City, ...

Moorten's Mill
"Cactus" Slim Moorten built a 5-stamp mill here in 1934 to process gold ore from 3 claims he had in the Cottonwood Spring area. Abandoned in 1939 little ...

Calico Ghost Town History
At first the ore from the Silver King Mine was hauled to Oro Grande, 40 miles away, but in 1882 a ten-stamp mill was erected beside the Mojave River at ...

Garlock Ghost Town
In 1894 Eugene Garlock of Tehachapi moved in an eight stamp mill. Miners would talk of going down to "the Garlock mill," "down to the Garlock," and finally ...

Lucky Baldwin/ Gold Mountain Mine, Big Bear - San Bernardino
...San Francisco multimillionaire, Elias J. "Lucky" Baldwin started a "gold rush" in 1874 when he constructed a large 40 stamp mill at the base of "Gold ...

Winona Mill - Joshua Tree National Park, Colorado Desert
...winona stamp mill photos - joshua tree national park, mojave desert. ... Winona Mill Cottonwood Spring Colorado Desert Mastodon Peak ...