James A. and Corale L. Brierley

Corale and James Brierley

Corale and James Brierley at Tronador Mountain, Argentina, in September 2009. Courtesy Corale Brierley.

For hundreds of years chemists have been going after gold—figuring out ways to find, gather, and use it. The husband-and-wife team of James A. Brierley (b. 1938) and Corale L. Brierley (b. 1945) gather particular microbes and get them to digest unwanted materials in gold ore, leaving the gold behind. Their method is cleaner and more efficient than traditional methods for mining precious metals and other minerals.

Born in Denver, Colorado, James Brierley chose to study microbiology, not chemistry. He began his academic career at Colorado State University, receiving a bachelor’s degree in bacteriology in 1961. He then proceeded to Montana State University, where he received a master’s degree in bacteriology (1963) and a doctor’s degree in microbiology (1966). As part of his doctoral research he studied microorganisms in the acid hot springs of Yellowstone National Park. There he discovered the microbe named after him, Acidianus brierleyi, that oxidizes sulfur-containing materials as a food source, just as humans and many other animals oxidize carbon-containing compounds.

Corale Brierley grew up on a cattle ranch in rural Montana and began her college education at Montana State University, where she met and married James. In 1966 the two set out for the New Mexico Institute of Mining and Technology, where he took a faculty appointment and she earned her B.S. in biology (1968) and M.S. in chemistry (1971). After graduating, she went to work teaching and researching at the university and at New Mexico’s on-campus bureau of mines.

Biohydrometallurgy was becoming a hot research topic due to the activities of these two scientists and others. It is an environmentally friendly method of extracting valuable metals from the substances in which they naturally occur. In nature, metals like gold, copper, iron, and zinc are usually found in combination with other substances, minerals in particular. Biohydrometallurgy uses tiny biological organisms, such as bacteria, and water to trigger chemical reactions that separate the metals from the minerals, all without giving off as much of the noxious byproducts that traditional methods produce. Bioleaching was carried out for centuries in China and the West, using mine slurries that had been naturally colonized by iron- and sulfur-eating microbes—unknown to be sure to the mining experts. The modern era of biohydrometallurgy began in 1958 with Kennecott Mining Company’s use of Thiobacillus ferrooxidans (since renamed Acidithiobacillus ferrooxidans) to process low-grade copper ores for metal extraction.

Six years after receiving her master’s degree Corale went back to school and graduated in 1982 with a Ph.D. in environmental science from the University of Texas at Dallas. She decided to go into business and started a company called Advanced Mineral Technologies. She managed the company, which employed 23 scientists and engineers, raised capital, did marketing, and patented innovations, while her husband served as research director. This company failed in the stock market crash of 1987. James then went to work for a gold-mining firm, Newmont Mining Corporation, while Corale managed the debt and intellectual property from their failed venture, wrote academic papers, edited a book, and eventually joined Newmont as chief of environmental process development. In 1991 Corale went back into business for herself, and her husband joined her in 2001 after retiring from Newmont. This new venture, Brierley Consultancy, specializes in designing innovative biohydrometallurgical processes and providing expertise to mining companies around the world.

Both Brierleys are elected members of the National Academy of Engineering.

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