Hendy Stamp Mill / Hendy's "California" Stamp Mill
Hendy Stamp Mill
During the California Gold Rush, Hendy Iron Works built mining and stamp mill machinery exclusively. They supplied mining operations around the world with 5-stamp mills that could operate as a single unit or as multiple units of up to 100 stamps, with 20 – 40 stamps as the most common installation.
Following the 1906 Earthquake, John Hendy moved the iron works from San Francisco to Sunnyvale, lured here by the offer of free land, and was operational in 1907. Hendy Iron Works was the first heavy industry in Sunnyvale and was Santa Clara Valley’s largest manufacturing concern at that time.
This Hendy “California” stamp mill represented the finest machine technology available in the early nineteen hundreds. This type of gravity stamp mill was one of the most important factors in the extraction of gold, silver and copper ores, from hard rock mines.
The stamp battery was activated by rotating the pulley wheel, made of a dried California Yellow Pine, which turned the camshaft and cams, made of “Adamantine” chrome steel, at 50 to 55 RPMS. The cams raised the 1,000 lb. stamps to a pre-set height. Then the stamps would fall, pulverizing the gold ore between the stamp heads and the mortar dies. The pulverized ore was sifted by a special screen placed across the front of the mortar so the precious metal could be retrieved. It could take as much as 50 tons of ore-bearing rock to recover as little as 2 ½ ounces of gold.
“The reputation and superiority of ‘Hendy’ mortars is based on experience, design and quality, to the interested engineer, investor or miner. This results in the best gravity stamp battery units of five stamps and over.”
Source: Henry Iron Works Catalog – July, 1911.
Hendy’s “California” Stamp Mill
This 5-stamp mill was built by Joshua Hendy Iron Works in Sunnyvale around the year 1918. Frederick W. Peterson purchased the mill in 1919 and began stamping out a family fortune at his gold mine in Pine Grove, California.
In 1986 the mill was purchased by the Iron Man Museum of Sunnyvale from Frederick’s great-grandson, Eric.
The restoration and installation of this mill was completed in April of 1996 through the efforts of the Iron Man Museum, the Sunnyvale Historical Society and Museum Association, Mountain Charlie Chapter 1850 – E Clampus Vitus and many members of the Community.
Dedicated May 11, 1996
A gift to the City of Sunnyvale and its citizens
Marker can be reached from North Sunnyvale Avenue near East California Avenue.
Courtesy hmdb.org
