John M. Callow (1867 – 1940)

Metallurgist & Inventor

2024 Inductee from Mining’s Past

John Michael Callow was born on July 7, 1867 in Northrepps, Norwich, Norfolk, England. He was a mining engineer and metallurgist. He was awarded the Douglas medal by the American Institute Mining and Metallurgical Engineers, 1926, for achievements in non-ferrous metallurgy. Callow came to the United States in 1890. He is the originator of pneumatic flotation in treatment of ores. The Callow flotation machine was one of the leading flotation machines for the first few decades of flotation. Callow's discoveries stimulated the development of mining in areas previously considered economically marginal. Callow was awarded 18 patents during his career.

He began his career as an engineer and draftsman with Stearns, Roger Manufacturing Company in 1892. He moved to  the Metallic Extraction Company, in 1894 as an engineer and operated mines and mills in San Juan County, Colorado from 1895-1896. He was on the engineering staff at Samuel Newhouse from 1898-1901 and entered into private practice from 1901-1906, inventing the Callow settling tank and Callow traveling belt screen. He then started the General Engineering Company of Salt Lake, New York and London in 1906.  As President and manager, he built up a network providing a wide variety of metallurgical expertise throughout the United States, Canada, Mexico and England. He retired in 1933.

He designed and built a 500-ton per day plant for National Copper Company, Mullan, Idaho, installing pneumatic flotation cells in 1912. He was the designing and construction engineer for Mount Isa Mines in Australia from 1928-1931 during its initial construction.

Callow died at his home in Redhill, Surrey, England in 1940. 

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