New rare earth age for old NY iron mines
Industrial Age waste may offer vital Information Age metals Metal Tech News – December 30, 2020
Last updated 12/29/2020 at 4:53pm
Industrial Age iron mines in the eastern Adirondack Mountains of Upstate New York may find new life as domestic sources of the rare earth elements needed in today's Information Age.
Mined heavily for iron in the 1800s and early 1900s, the eastern Adirondack Mountains played an important role in industrialization prior to and during World War II. The deposits that helped to build America's transformation from horse powered to horsepower also happened to host significant amounts of rare earths, a group of 17 elements now being used to build the modern era of data and technology.
Today, rare earths are used in a wide array of high-tech devices – smartphones, computers, electric vehicles, wind turbines, medical imaging devices, and lasers are a small sampling of the uses for these elements.
With the U.S. highly dependent on China for rare earths, federal agencies have been seeking potential domestic sources. The drive toward American rare earths independence led the U.S. Geological Survey to investigate the potential of tailings and other waste rock left behind from mining iron from the Adirondack Mountains as a domestic source of these technology elements.
"The possibility of accessing rare earth elements from mine waste and mill tailings is attractive partly because the minerals have already been excavated from the ground," said Ryan Taylor, the USGS scientist that led analyses of rock samples from the region. "This would reduce mining costs by making it easier to access the minerals. It also allows 'recycling' of discarded materials, which could help to remediate these mined areas."
USGS first identified rare earths in the tailings and waste dumps of Upstate New York iron mines in the 1950s. At that time, however, there was virtually no use for these elements. It really was not until the advent of color televisions in the 1960s that some rare earths found commercial use and over the ensuing six decades, the unique properties offered by this group of 17 elements are being leveraged to make modern tech devices, smaller, smarter, greener, and more powerful.
With rare earths becoming increasingly critical to Information Age technologies, USGS began carrying out airborne geophysics and on the ground investigations to better understand the potential of these elements left behind by iron miners of a bygone era.
Mining of these technology metals would offer the added benefit of improved aesthetics and environment through modern reclamation and restoration techniques.
"This inspired the USGS, New York state, and local groups to work together to analyze waste rock and tailings," said U.S. Geological Survey Director Jim Reilly. "We look forward to future collaborations with them and potentially other states in this emerging area of study."
The rare earths in the Adirondack Mountains mine tailings, as well as unmined deposits in the area, are mostly contained in millimeter-size crystals known as fluorapatite that was usually left behind as waste because it was considered an unwanted impurity.
This calcium-phosphorous-fluorine mineral, however, has elevated levels of gadolinium, used in medical imaging; terbium, used in smartphones; and yttrium, used in lasers. These and the other heavy rare earths tend to be far less common than the light rare earths.
Sampling carried out by the USGS found that waste rock and tailings piles left behind by Industrial Age miners in the Adirondack Mountains contain up to 2.2% rare earths and unmined deposits have as much as 4.8% rare earths.
The federal geologists say these grades are comparable to the clay deposits that are the primary sources for China's and, as an extension, the world's heavy rare earth elements.
These grades are also higher than those reported for coal fly ash left behind by decades of coal-fired power generation that is also being considered as a potential domestic source of rare earths.
"There may be some challenges to processing the tailings for rare earth elements," said Anji Shah, A USGS scientist and head of the eastern Adirondack Mountains rare earths project. "While the fluorapatite contains recoverable rare earth elements, it also contains thorium, a weakly radioactive element which has economic uses but also requires careful handling."
That same thorium, however, makes mill tailings easier to locate by airplane surveys since the natural, low-level radioactivity in the fluorapatite is easy to identify with imaging.
The airplane surveys were also able to easily detect the iron deposits themselves due to the highly magnetic crystals of magnetite that make up the ore. By measuring subtle variations in Earth's magnetic field from the sky, the researchers created 3D models showing the size and shape of the deposits beneath Earth's surface.
These modern geophysical survey techniques show the iron deposits are much larger and deeper than previously realized, providing potential sources of rare earths below those in the waste piles left behind by Industrial Age miners.