Pebble adds rhenium to world-class titles
Alaska deposit hosts Earth's largest store of rare critical metal Metal Tech News – August 26, 2020
Last updated 6/8/2023 at 12:12pm
While the recent call from conservationists and sportsmen for the Trump administration to block permits has cast a shadow of doubt on the development of a mine at Pebble, there is no denying the controversial Alaska project encompasses a world-class store of precious, industrial and critical minerals.
A recent recalculation of the Pebble resource shows the deposit hosts roughly a third of the world's known rhenium, an extremely rare metal that lends its exceptional heat resisting qualities to superalloys used in the jet turbines that ensure commercial and military aircraft stay airborne.
"More than 80% of the rhenium consumed in the world is used in high-temperature superalloys, especially those used to make turbine blades for jet aircraft engines," the United States Geological Survey penned in a 2018 report on critical minerals.
This heat resistant metal, however, is one of the rarest stable elements on the periodic table, averaging less than 1 part per billion in the Earth's crust.
While exceptionally rare and never found concentrations to mine as a standalone metal, rhenium is often found clinging to molybdenum minerals in porphyry deposits, which are the source of most of the copper mined globally.
Pebble happens to be one of the largest porphyry copper-gold-silver-molybdenum, and now rhenium, deposits ever discovered on Earth.
This world-class deposit, however, happens to be near the equally world-class Bristol Bay salmon fishery. This juxtaposition of pre-eminent resources has many calling for extraordinary measures to ensure a Pebble Mine does not endanger the Southwest Alaska salmon fishery.
Critical superalloy metal
The United States imported more than 80% of the 47,000 kilograms of rhenium used by American manufacturers during 2019. Most of this metal went into high-temperature superalloys needed for the jet turbines of commercial and military aircraft.
"The high-temperature properties of rhenium allow turbine engines to be designed with finer tolerances and operate at temperatures higher than those of engines constructed with other materials," USGS penned in a fact sheet on the critical metal. "These properties allow prolonged engine life, increased engine performance, and enhanced operating efficiency."
The other major use of rhenium, which accounts for about 10% of worldwide rhenium consumption, is in platinum-rhenium catalysts used to boost the octane level of refined gasoline and improve refinery efficiency.
This rare metal also lends its heat resistance to electrical contact points, flashbulbs, heating elements, vacuum tubes, and X-ray tubes.
While rhenium offers superior heat tolerance to alloys, aircraft and other manufactures limit their use of this metal due to the high price driven by its scarcity.
World-class rhenium lode
While the Pebble Mine project in Alaska has long been known to host rhenium associated with the molybdenum minerals in the deposit, an official resource of this critical superalloy metal had never been calculated – until now.
A new estimate published by Northern Dynasty Minerals Ltd., the company advancing exploration and permitting at Pebble, outlines roughly 4.2 million kilograms (9.3 million pounds) of rhenium in all resource categories at its Alaska project.
According to this new calculation, Pebble hosts 6.5 billion metric tons of measured and indicated resources averaging 0.4% (57 billion lb) copper, 0.34 grams per metric ton (71 million ounces) gold, 240 parts per million (3.4 billion lb) molybdenum, 1.7 g/t (345 million oz) silver and 0.41 ppm (2.6 million kg) rhenium.
The world-class porphyry deposit in Alaska also hosts 4.5 billion metric tons of inferred resource averaging 0.25% (25 billion lb) copper, 0.25 g/t (36 million oz) gold, 226 ppm (2.2 billion lb) molybdenum, 1.2 g/t (170 million oz) silver and 0.36 ppm (1.6 million kg) rhenium.
Considering rhenium is one of the rarest stable elements on the periodic table, this is an enormous store of the critical metal. By way of comparison, the United States Geological Survey calculated the total amount of rhenium in global resources at 11 million kg at the end of 2019. This means the new calculation for Pebble has bolstered the world's known rhenium resources by roughly 38%.
Pebble also happens to be the largest undeveloped copper and gold deposit on Earth.
Roiled in controversy
The Pebble project, however, has been roiled in controversy due to its proximity to Bristol Bay, home to a world-class salmon fishery in Southwest Alaska.
With a federal permitting decision for Pebble expected soon, an influential group with close ties to the White House have suggested that President Trump should err towards environmental conservation when it comes to Bristol Bay and the Pebble Mine.
"We've seen a small number of unelected but high-profile conservatives suggest President Trump should put his thumb on the scale when it comes to the final step of permitting at Pebble – the record of decision, we're expecting within weeks," said Tom Collier, CEO of Pebble Limited Partnership, an Alaska-based subsidiary of Northern Dynasty.
These rumbling gained national attention when President Trump's eldest son, Donald Trump Jr., weighed in on the conservation side of developing a mine at Pebble.
"The headwaters of Bristol Bay and the surrounding fishery are too unique and fragile to take any chances with," Trump Jr. tweeted.
When asked by a reporter about Trump Jr.'s suggestion this administration should reject the Pebble Mine, President Trump said, "I don't know of the argument yet, but I would certainly listen to both sides, my son has very strong opinions, and he is very much an environmentalist."
Others close to the White House, including Andy Sabin, a major Trump campaign contributor has reportedly also weighed in on the conservation side of the Pebble argument.
While the Trump administration has not outright rejected Pebble, a memo sent out by the U.S. Army Corps of Engineers, which is overseeing the federal permitting of the mine, has called for strict mitigation requirements to offset the wetlands disturbed by the mine project. These requirements, detailed in a memo sent to the Pebble Partnership on Aug. 24, will need to be met before the Corps can issue key federal permits for Pebble.
Conservative groups, such as Americans for Limited Government, are urging the Trump administration to make Pebble a top priority.
"This administration has put a premium on ending our dependency on China for rare earth metals, and now in the wake of the announcement that rhenium, a key component to aircraft engines, was discovered at the Pebble mine, this makes the development of Pebble mine a national security must," said Americans for Limited Government President Rick Manning.
"This is both good national security and resource development policy, and meets the President's priorities," he added.
Critical domestic deposit
If Pebble Partnership can gain the federal permits and then gains state permits, which is expected to take about another two to three years, a mine at the Southwest Alaska project could become a significant domestic source of many metals needed in the U.S.
"There's absolutely no doubt there is growing domestic and international market demand for the metal commodities Pebble will produce," Collier said. "Whether it's surging demand for copper to facilitate the US and global transition to a low carbon future, the increasing demand for gold we're seeing in the current economic climate or the other strategic metals our mine will produce, the world needs Pebble."
America's transition away from fossil fuels and toward renewable sources of power will be particularly copper-intensive, as will the requirement for smart grid technology to make the nation's energy transmission and distribution system more efficient.
Electric vehicles, solar and wind power installations, as well as the energy infrastructure required to enable these technologies, will all require substantially more copper than the transportation and energy systems they replace.
World Bank estimates that roughly 550 million tons of copper will be needed for generating and transmitting electricity over the next 25 years, which is nearly as much as humans have mined over the past 5,000 years.
More information on World Bank's forecast for the demand of minerals and metals needed for renewable energy can be read at All clean energy paths lead to mining in the May 13 edition of Metal Tech News.
In addition to the world-class lode of copper and other metals outlined in the resource, Pebble hosts considerable quantities of palladium, a precious metal used in fuel cells, catalytic convertors, and other applications; and tellurium, an extremely rare metalloid that is a vital ingredient to emerging solar panel technologies.
The U.S. currently imports 35% of its annual copper needs from foreign producers, as well as 32% of its palladium, 82% of its rhenium, 68% of its silver, and more than 95% of its tellurium.
"It is in the United States' best interest to develop reliable and long-term domestic sources of mineral commodities like copper, gold, molybdenum, silver, rhenium and palladium – strategic metals that are critical to the country's economic, energy, military and industrial future," Collier said. "It is equally important to source these minerals from jurisdictions that are known to be leaders in environmental protection, in conserving healthy fish and wildlife populations, as well as in environmental justice and human rights. That description fits Alaska to a tee and is one more reason why Pebble is poised to become one of America's leading metals producers."
First, however, the Pebble Partnership must demonstrate to U.S. and Alaska regulators that a mine at Pebble can be developed without endangering the Bristol Bay salmon fishery.