North of 60 Mining News - The mining newspaper for Alaska and Canada's North

America's supply of tungsten, an extremely durable metal that is vital to a broad range of American industrial sectors, is at high-risk.

A recent U.S. Geological Survey assessment to identify which mineral commodities are most at risk to supply disruptions ranked tungsten near the top of the list – alongside rare earth elements, cobalt and graphite, platinum group metals and tungsten.

Like many of its neighbors at the top of the mineral commodity supply risk list, much of the potential for supply disruptions has to do with China's near monopoly on mining this tough metal.

"World tungsten supply was dominated by production in China and exports from China," USGS penned in its 2020 Mineral Commodity Summaries.

According to this annual report, China accounted for more than 80% of the 85,000 metric tons of mined tungsten produced globally during 2019.

This provides the Middle Kingdom with a strong hand when it comes to controlling pricing and global supply, something the country has been known to use to maintain and strengthen its control over metals supply.

"China's government regulated its tungsten industry by limiting the number of mining and export licenses, imposing quotas on concentrate production, and placing constraints on mining and processing," according to the USGS.

Despite being dependent on China and other countries for much of its tungsten supply, the U.S. has significant unmined tungsten resources. Much of these resources are found in Alaska, a state that has previously provided a domestic supply of the tungsten minerals wolframite and scheelite in times of need.

Demanding durability

Extremely hard and with the highest melting point of all the elements on the periodic table, tungsten is vital to a broad spectrum of commercial and military applications, yet there are no American mines producing this durable metal. Instead, the U.S. depends on recycling and imports to meet its tungsten needs.

As a stopgap, the U.S. government has also been supplementing American tungsten supply out of its stockpiles. According to USGS data, roughly 3,390 metric tons of tungsten has been sold out of government stockpiles since 2017.

Nearly 60% of the tungsten consumed in the U.S. during 2019 was used to make the cemented tungsten-carbide, a compound of roughly equal parts tungsten and carbon.

Roughly twice as strong as steel, tungsten carbide is often found on the working end of drill bits, saw blades, wear plates and other items that require this compounds toughness to meet some of the most demanding conditions in the mining, oil and gas, construction and metal-working industries.

Tungsten carbide's hardness and density also makes this metallic compound ideal for making armor-piercing ammunitions for the military.

Because it retains its strength at high temperatures, elemental tungsten is also used in many high-temperature applications. Heating elements, lightbulb filaments, rocket engine nozzles and TIG (tungsten inert gas) welding are among the many applications that take advantage of tungsten's ability to hold up to heat.

Wise Mike discovery

While there is not any tungsten produced in the United States today, this hard, industrial metal has been historically mined in several locations across Alaska.

The gold-rich hills around Fairbanks, in the heart of Alaska's Interior, is one of the past producing tungsten regions.

In 1915, Balkan immigrant "Wise" Mike Stepovich discovered hardrock tungsten mineralization on the eastern flank of Gilmore Dome about 15 miles northeast of Fairbanks, which is near Kinross Gold Corp.'s currently producing Fort Knox gold mine.

Over the ensuing three years, Stepovich and his crew dug more than 2,000 feet of underground workings and produced 300 tons (600,000 pounds) of high-grade tungsten ore averaging 8% tungsten and 10 tons of concentrates that averaged about 65% tungsten trioxide.

With a substantial drop in tungsten prices at the end of World War I, however, Stepovich put a halt to his hardrock tungsten operations to resume mining the rich deposits of placer gold near Fairbanks, which is what drew him to Interior Alaska in the first place.

Stepovich's discovery, however, sparked interest in the region's tungsten potential.

"The scheelite deposits of the Fairbanks district are believed to be much more extensive than the surface outcrops show and to give promise of a large future production of tungsten," the USGS wrote in its 1917 Mining in the Fairbanks District report.

While this promise has yet to be fully realized, World War II rekindled interest in the tungsten around Fairbanks. In 1942, Cleary Hill Mines Co. leased the properties covering the tungsten lode from Stepovich and produced another 43,920 pounds, or nearly 22 tons, of tungsten trioxide.

All of Cleary Hill Mines' World War II production was sold to the Metals Reserve Company, a subsidiary of the federal government-backed Reconstruction Finance Corp. in Washington D.C.

Several other tungsten deposits and prospects were identified near Stepovich's discovery, including the Colbert lode, and Yellow Pup and Schubert prospects.

In the late 1970s and early 1980s, several tons of high-grade tungsten concentrates were shipped from Yellow Pup and un-milled ore was stockpiled there.

Shorty Creek find

While the Fairbanks Mining District is a past producer of tungsten, it is not the only area of Alaska's Interior region where this critical hard metal can be found.

About 70 miles north of Fairbanks, Freegold Ventures Ltd. has discovered tungsten alongside the copper, gold, and silver on its Shorty Creek property in the Livengood Mining District.

Freegold identified the tungsten potential at Shorty Creek during a 2016 drill program to expand upon the porphyry mineralization associated with a large magnetic high geophysical anomaly at the Hill 1835 target on the property.

The first hole drilled that year, SC 16-01, cut 207 meters averaging 0.045% tungsten trioxide; and the second, SC 16-02, cut 409.6 meters averaging 0.03% tungsten trioxide.

In addition to tungsten, continued drilling at Hill 1835 has tapped cobalt, a critical battery metal, with the copper, gold, and silver in this porphyry target.

Drilled about 200 meters southwest of the 2016 intercepts, hole SC 17-01 cut 360 meters averaging 0.24% copper 0.07 g/t gold, 4.04 g/t silver, 100 parts per million cobalt and 0.03% tungsten trioxide.

SC 17-02, drilled in the same area, cut 408 meters averaging 0.27% copper 0.05 g/t gold, 4.97 g/t silver, 85 ppm cobalt and 0.05% tungsten trioxide.

Hole SC 17-03, which was lost at a depth of 362.2 meters in strong mineralization due to mechanical difficulties, cut 105.2 meters averaging 0.27% copper, 0.05 g/t gold, 6.75 g/t silver, 114 ppm cobalt and 0.06% tungsten trioxide.

The mix of base, precious and critical minerals at Shorty Creek has drawn the interest of Australian major South32 Ltd., which has agreed to invest up to US$10 million to this road-accessible property over a four-year span beginning in 2019.

Hints of tungsten

Considering the amount of tungsten showing up in placer gold mining concentrates, often called black sands due to the color of this heavy material captured in sluice boxes and other gravity gold recovery systems, tungsten is common across Alaska's Eastern Interior.

"The Circle Mining District, including the Birch Creek area, has been known for years for its tin (cassiterite) and tungsten (wolframite and scheelite) minerals occurring in gold placer concentrates," James Barker penned in a 1979 U.S. Bureau of Mines report, "A trace element study of the Circle Mining District."

Barker's investigation found tungsten in most streams draining the Circle Hot Springs granitic intrusive, which is also the source of much of the gold in the heart of the Circle Mining District.

Sampling in the Lime Peak and Mount Prindle areas west of the intrusive also turned up tungsten and tin mineralization.

While the load source of tungsten in the Circle Mining District has not been identified, a sample of fresh granite collected by Barker at the upper end of Boulder Creek, a stream known for its heavy tin mineralization, returned 22 ppm tungsten, 20 ppm tin, as well as gold and molybdenum.

Mother Nature has already milled and concentrated these critical metals in Boulder and other creeks in the area.

"Minable deposits of placer tin-tungsten minerals may exist in the Circle Mining District," Barker concluded.

The Fortymile Mining District, located between the Circle District and Yukon's famed Klondike District, also has some interesting tungsten occurrences.

Doyon Ltd., an Alaska Native corporation representing more than 19,000 shareholders that have called Alaska's Interior home for millennia, owns tungsten prospective lands in the Fortymile.

These prospects, Duval Creek and Happy, were identified during investigations of the area in the 1970s.

Anomalous tungsten was discovered in stream-sediment and heavy-mineral concentrates in Duval Creek on what is now Doyon land during reconnaissance sampling in 1978.

Scheelite and molybdenite were discovered at Happy, located near Duval Creek, around the same time. Float boulders of quartz veins collected at Happy contained as much as 0.82% tungsten and 0.3% molybdenum.

These hints of tungsten add to the future potential of the Circle and Fortymile mining districts, regions of Interior Alaska that have produced some 2 million oz of placer gold.

Lost River discovery

Much like its gold rush counterparts in Alaska's Interior, streams in the Nome area of western Alaska host intriguing amounts of placer tungsten. Lost River, a skarn deposit about 85 miles northwest of Nome, is particularly enriched with tungsten and other critical minerals.

The significant amount of tin found in the aptly named Cassiterite Creek led early miners and prospectors to the Lost River deposit around 1902 and small-scale underground mining began there shortly after the discovery.

At the time, the tin found in this deposit was the target of mining. The tungsten, fluorite (or fluorspar) and beryllium also discovered there – all currently considered minerals critical to the United States – were largely ignored.

This mix of metals drew the interest of Lost River Mining Company, which planned to mine the mix of critical metals there in the 1970s.

In preparation for developing a mine, roughly 16,100 meters of drilling in around 110 holes were drilled into the Lost River skarn.

Based on this drilling, it was estimated that the deposit hosts some 23.53 million short tons of resource averaging 16.43% fluorite, 0.26% tin, and 0.04% tungsten trioxide that could be mined by open pit methods; and 1.28 million tons of 11.66% fluorite, 0.15% tin, and 0.01% tungsten trioxide considered more suitable for underground mining.

According to this historical estimate, the surface minable portion of the Lost River deposit hosts 18.84 million lb of tungsten, 7.7 billion lb of fluorite, and 122 million lb of tin.

Beryllium is also reported to be associated with this deposit but is not reported as a resource due to the difficulties recovering it.

Geologists familiar with Lost River, however, caution that further work needs to be done to shore up the historical estimate due to the spatial and mineralogic complexities of the deposit.

Considering Lost River hosts four metals considered critical to America's economic and strategic security, the extra work needed to determine just how much tungsten, tin, fluorite, and beryllium the deposit contains may well be worth the effort.

Tungsten ghost mine

Interior is not the only region of Alaska to produce tungsten in times of American need. During World War II, this critical industrial metal was also extracted from the zinc-lead-copper concentrates produced from the Riverside Mine in the Hyder District of Southeast Alaska.

Located just across the border from Stewart, a British Columbia mining town at the southern tip of the Canadian province's famed Golden Triangle, the Hyder District experienced a boom of mining activity in the 1920s. While most mining in this region at the southern end of the Southeast Alaska panhandle faded in the 1930s, the Riverside Mine was revived in 1940.

Records show that 70,000 lb (35 tons) of tungsten, 3,000 oz of gold, 100,000 oz of silver, 100,000 lb of copper, 250,000 lb of lead and 20,000 lb of zinc was recovered from 30,000 tons of ore mined at Riverside.

At least six prospects – Last Shot, Mountain View, Fish Creek, Blue Bird, Monarch and Last Chance – have been identified across a 1.5- by three-mile area near the Riverside Mine, about 5.5 miles north of the town of Hyder.

While mining and mineral exploration is prolific around Stewart, there has been virtually no mining in the Hyder District just across the Alaska-B.C. border since the closing of the Riverside Mine.

The less than 100 current residents of Hyder embrace this disparity with the motto "the friendliest ghost town in Alaska."

Huge off-limit discovery

The largest deposit of tungsten in Alaska may lie in the Bear Mountain occurrence along the southern slopes of the Brooks Range.

During visits to Bear Mountain in the 1980s, Barker and fellow U.S. Bureau of Mines geologist R.C. Swainbank identified a 100-acre area of surface mineralization indicative of a large porphyritic molybdenum-tungsten deposit.

Analysis of 20 soil and 36 rock samples collected during 1985 returned abundant tungsten and molybdenum along with lessor amounts of niobium.

Soil samples collected over roughly 75-acres returned tungsten values of more than 500 ppm wolframite, with the best samples containing 5,000 ppm of this tungsten mineral.

"I believe Bear Mountain to be likely the most important tungsten deposit in the U.S.," Barker told Mining News.

James Barker

Bear Mountain northeast Alaska may host one of the largest tungsten deposits in the United States.

The potential of this intriguing tungsten-molybdenum discovery, however, may never be realized due to its location.

In addition to being located in a remote corner of northeast Alaska, this potentially world-class tungsten-molybdenum deposit is situated within the Arctic National Wildlife Refuge, or ANWR, a 19.3-million-acre region set aside for wilderness and wildlife conservation.

"It's a shame that mineral evaluations aren't done before we place an area off limits," Barker reflected.

While Bear Mountain tungsten, molybdenum and niobium may be stored in an off-limits reserve, there are mines in Alaska that have answered America's urgent call for tungsten in the past and the state hosts many more that could answer a similar call should a pressing need for the durable industrial metal rise again in the future.

Author Bio

Shane Lasley, Publisher

Over his more than 16 years of covering mining and mineral exploration, Shane has become renowned for his ability to report on the sector in a way that is technically sound enough to inform industry insiders while being easy to understand by a wider audience.

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