(4) Swallow Mine 5-Stamp Restoration Project

History of the Swallow Mine Stamp Mill: This stamp mill was used to crush gold bearing ores and deposit the fine gold on mercury coated copper plates. It is 19 feet tall, and the large drive wheel is 7 feet in diameter. The mill was operated by a 50 horse Western States single cylinder engine. The large metal structure at the base is called the mortar box, which contains the ore while it is being crushed. Water is used to move the materials out of the mortar box to a copper plate coated with mercury to absorb the gold as it leaves the mill. Each vertical rod (stamp) weighs 850 pounds and the stamp drops 120 times per minute from a height of 4 to 6 inches. The stamp mill operation crushes about 8 tons of ore in a 24 hour period.

This 10-stamp mill was originally installed during the 1890's at a small town called Briggs near Castle Creek, approximately three miles from the Swallow Mine. In the beginning the ore was transferred from the Swallow Mine to the mill, but after a few years the mill was disassembled and taken directly to the Mine where only 5 of the stamps were used. There are only two years of documented operation of the stamp mill during its service at the Swallow Mine. The first 1000 tons of material through the mill ran about $60.00 of gold per ton, or about 2 oz. gold per ton.

The picture below was taken in 1986 shows the stamp mill at the Swallow Mine before it was brought back to Phoenix. The mill was already partially disassembled when it was donated to the museum.

Millsite at Swallow Mine

 

Disassembly, Transport and Reassembly: This was the first stamp mill and second major project that I was involved with at the Arizona Mining & Mineral Museum. The stamp mill was donated to the Arizona Mining & Mineral Museum by the owner of the Swallow Mine, Charles C. Brown of Sun City.

The restoration process took from April 1996 to March 2003. This included disassembly of the mill, transporting the components from the mine 17 miles north of Wickenburg, AZ to downtown Phoenix, and assembly of the mill with all of the utilities. The job was completed with the help from Arizona Public Service Hauling Services and the Monday Crew, a group of about 10 to 12 volunteers that completed most of the work. This restoration process included sandblasting and painting all of the metal surfaces. Instead of using the gasoline engine a 15 Hp electric motor was used. A jackshaft was also incorporated to reduce the speed down to 60 RPM at the bull wheel. The original timbers were used after a cosmetic restoration was completed on the timbers surfaces.

This mill could be considered a “production mill”, since it has all of the attributes of an operational mill. This includes a rotational speed of 60 RPM, a 4” to 6” stamp drop, an operable automatic Hendy feeder, sluice tables with riffles and miners moss and fed with “gold bearing ore”.   I have found very few mills in the United States that could be considered production mills.

Installation at Downtown Phoenix