The Holt-Dern process is method by which silver and gold can be extracted from low-grade ores. This book appears to be in the

public domain The public domain (PD) consists of all the creative work A creative work is a manifestation of creative effort including fine artwork (sculpture, paintings, drawing, sketching, performance art), dance, writing (literature), filmmaking, ...

as a work of the United States government. The method was applied in mining at

Park City, Utah Park City is a city in Utah, United States. The vast majority is in Summit County, and it extends into Wasatch County. It is considered to be part of the Wasatch Back. The city is southeast of downtown Salt Lake City and from Salt Lake City' ...

and in the Tintic Mining District, specifically at the

Tintic Smelter Site The Tintic Smelter Site, located off U.S. Route 6 near Silver City, Utah, United States, that is listed on the National Register of Historic Places (NRHP). Description The site is one of few legacies of historic Silver City, a mining boom town ...

. It was named for

George Dern George Henry Dern (1872–1936) was an American politician, mining man, and businessman. He co-invented the Holt–Dern ore roasting process and was United States Secretary of War from 1933 to his death in 1936. He also served as the sixth Gov ...

and T.P. Holt.

References

{{reflist Chemical processes Mining techniques Smelting