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By Shane Lasley
Mining News 

Critical Minerals Alaska – Tungsten

Hard evidence of past production, prospects found across state

 

Last updated 8/17/2018 at 5:52am

Critical minerals Alaska Lost River Stepovich Gilmore Dome Fairbanks

Mike wai, Creative Commons

Tungsten carbide is used to make core drilling bits used by the mining industry, such as the Atlas Copco bit on the left. Diamond impregnated bits, such as the two on the right, however, are the most common choice for hard rock drilling.

Extremely hard and with the highest melting point of all the elements on the periodic table, tungsten is a vital ingredient to a wide-range of industrial and military applications, yet none of this durable metal is currently mined in the United States.

According to the United States Geological Survey, more than half of the tungsten consumed in the U.S. last year was used to make the cemented tungsten-carbide, a compound typically made with equal parts tungsten and carbon.

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

Tungsten carbide's hardness, coupled with its very high density, also makes this metallic compound ideal for making armor-piercing ammunitions for the military.

Because it retains its strength at high temperatures and has a high melting point, elemental tungsten is used in many high-temperature applications, such as light bulb, cathode-ray tube and vacuum tube filaments; heating elements; and rocket engine nozzles

Its high melting point also makes tungsten suitable for aerospace and high-temperature uses such as electrical, heating, and welding applications, such as TIG (tungsten inert gas) welding.

Though none of this tough metal is currently mined in the United States, Alaska is a past producer of the tungsten minerals, wolframite and scheelite, and areas across the state show promise for future production of these and other critical minerals.

China dominates tungsten

Like most minerals deemed critical to the United States, China dominates mining and global supplies of tungsten.

In 2017, the Middle Kingdom produced an estimated 79,000 metric tons of tungsten, roughly 82 percent of the global total for the year. Vietnam, the world's second largest tungsten supplier, produced 7,200 metric tons last year. Russia, Austria and the United Kingdom round out the world's top tungsten sources.

In recent years, however, China has put limitations on tungsten mining and exports of this durable metal, causing concerns about global 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," the USGS penned in its annual report, Mineral Commodity Summaries 2018. "During 2016 and 2017, China's efforts to enforce production quotas, reduce illegal mining, and improve environmental conditions resulted in limited availability of tungsten concentrates in China."

While China touts stronger environmental safeguards as one of the primary reasons for restricting the mining of tungsten, as well as a host of other critical metals, many analysts believes the government's motives have more to do with consolidating mining to the country's largest producers and bolstering prices.

Whatever the motivations, China's production and export restrictions have resulted in sharp increases in the price of ferro-tungsten, an iron (25 percent) and tungsten (75 percent) alloy traded on world markets.

Going into 2017, ferro-tungsten was selling for around US$11.50 per pound. In early June 2017, the price jumped 13 percent to US$13/lb and has been steadily climbing ever since to the current price of US$14.24/lb. This, however, is significantly lower than the spike to a record US$24/lb in 2012.

USGS said that China's consumption of tungsten concentrates and production of finished products using the hardening metal has increased over the past couple of year. Which, in combination with supply restrictions, could continue to push prices upwards.

The United States consumed roughly $500 million worth of tungsten in 2017.

Tungsten mining around Fairbanks

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 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 percent tungsten and 10 tons of concentrates that averaged about 65 percent 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 report, "Mining in the Fairbanks District."

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 U.S. Government-owned Metals Reserve Company.

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.

Exploring Circle, Fortymile districts

While the Fairbanks Mining District is a past producer of tungsten, it is not the only Interior Alaska mining district to host this critical metal.

"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 from 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 Bedrock Creek, a stream known for its heavy tin mineralization, returned 22 parts per million tungsten, 20 ppm tin, as well as gold and molybdenum.

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

The Fortymile Mining District, situated just across the border from Yukon's famed Klondike District, also hosts some interesting tungsten occurrences.

Doyon Ltd., an Alaska Native corporation representing 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 percent tungsten and 0.3 percent 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.

Tungsten adds to Shorty Creek mix

Freegold Ventures Ltd. has found lode tungsten at its Shorty Creek property in the Livengood Mining District, about 70 miles north of Fairbanks.

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

SC 16-01 cut 207 meters averaging 0.045 percent tungsten trioxide; and SC 16-02 cut 409.6 meters averaging 0.03 percent tungsten trioxide.

Follow-up drilling last year continued to cut long sections of tungsten mineralization at Hill 1835, as well as the copper, gold, silver and cobalt also found at Shorty Creek.

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

SC 17-02, drilled in the same area, cut 408 meters averaging 0.27 percent copper 0.05 g/t gold, 4.97 g/t silver, 85 ppm cobalt and 0.05 percent 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 percent copper, 0.05 g/t gold, 6.75 g/t silver, 114 ppm cobalt and 0.06 percent tungsten trioxide on the eastern edge of the magnetic high at Hill 1835.

One hole drilled at Steel Creek, another large magnetic anomaly about 1,500 meters northeast of Hill 1835, also encountered copper, gold, silver, cobalt and tungsten. While the mineralization was only anomalous, this first hole drilled into the target provides evidence of the larger prospectivity across the road accessible property.

The mix of base, precious and critical minerals makes Shorty Creek a compelling project.

Friendliest tungsten ghost town

Interior is not the only region of Alaska to produce tungsten. 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 87 residents of Hyder embrace this disparity with the motto "the friendliest ghost town in Alaska."

Rediscovering the Lost River Mine

Of all the tungsten-bearing deposits in Alaska, the Lost River skarn on the Seward Peninsula about 80 miles northwest of Nome likely holds the most promise for developing a tungsten mine in Alaska.

The significant amount of tin found in the aptly named Cassiterite Creek led early miners and prospectors to the Lost Creek 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 found 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 develop a mine there in the 1970s.

In preparation for developing a mine, roughly 16,100 meters of drilling in around 110 holes was completed there at the time.

Based on this drilling, it was estimated that the Lost River skarn deposit hosts some 23.53 million short tons of resource averaging 16.43 percent fluorite, 0.26 percent tin, and 0.04 percent tungsten trioxide that could be mined by open pit methods; and 1.28 million tons of 11.66 percent fluorite, 0.15 percent tin, and 0.01 percent 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.

Alaska Critical Minerals Map tin tungsten

United States Geological Survey

This map shows regions of Alaska that are prospective for the specialized granites that carry tin and a host of other minerals considered critical to the United States, including tungsten. The areas in red are considered to have the highest potential.

With tungsten, fluorite, tin and beryllium all on USGS's recent list of minerals critical to the United States, the Lost River deposit may well be worth the work to further define a critical metals deposit on U.S. soil.

Editor's Note: "Critical Minerals Alaska – Tungsten" is the seventh of a series of articles being published in North of 60 Mining News that investigates Alaska's potential as a domestic source of minerals deemed critical to the United States. At least 29 of the 35 critical minerals and metals identified by the U.S. Geological Survey – antimony, arsenic, barite, beryllium, bismuth, chromium, cobalt, fluorspar, gallium, germanium, graphite, hafnium, indium, magnesium, manganese, niobium, platinum group metals, rare earth elements, rhenium, rubidium, scandium, tantalum, tellurium, tin, titanium, tungsten, uranium, vanadium and zirconium – are found in Alaska.

 

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