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

From the advancements of technology during the Bronze Age to the computers and telecommunication systems of today's Big Data Era, tin has been critical to human progress for at least 5,500 years.

Sometime around 3500 BC, Sumerians living in modern day Turkey and Iran discovered that mixing a little tin with copper created bronze, an alloy that produced much more durable weapons and tools than those cast from copper alone.

This cutting-edge discovery offered a strategic and economic advantage over those who did not possess the ingredients or skills to make this copper-tin alloy. The benefits offered by this metallurgical technology were so profound that we now consider the Bronze Age one of the most important epochs of human history, an era that spans more than 2,000 years.

Not unlike our Bronze Age forebearers, modern civilization continues to almost exclusively use tin in alloys, mixtures that keep tin on the list of critical minerals.

"Almost without exception, tin is used as an alloy," the United States Geological Survey penned in the tin section of a comprehensive 2018 report on critical minerals. "The major uses of tin today are for cans and containers, construction materials, transportation materials, and solder."

Glue of modern tech

While tin cans, cups, roofs, and foil may not conjure up images of a metal that should be considered critical to the technological wellbeing of a country like the United States, researchers from the Massachusetts Institute of Technology rank it as the most critical tech metal on Earth.

A 2018 Rio Tinto-commissioned study carried out at MIT found that tin beat out more likely technology metal candidates like lithium, cobalt, and graphite it when comes to being impacted by new technologies such as autonomous and electric vehicles, advanced robotics, renewable energy, and computers.

"Rio Tinto's Ventures group is looking for new areas to invest and tin is at the top of their list of metals likely to be positively impacted by new technology," the global miner informed colleagues during a 2018 battery metals conference in Australia.

One of the main reasons these high-tech sectors are putting so much demand on tin is the metal's use in solders that make the innumerable connections in electronics and electrical products.

"Tin's extensive use in solders makes it the metal that glues the technology revolution together, and new applications, such as in emerging lithium-ion batteries, tend to grow as technology advances and diversifies," said Roskill, a world-leading metals consultant based in London.

Roskill expects emerging tech applications such as the rollout of a global 5G network, smart home devices, and advances in lithium-ion batteries to drive growing demand for tin.

New supply is not keeping pace with these growing demands for this, pushing the price of this underappreciated techno-glue to new record highs.

After plunging to a low of around US$13,680 per metric ton in March, tin prices rocketed to US$34,993/t in July, shattering the previous all-time high for the alloying metal set in 2011.

There are, however, no U.S. tin mines to reap the benefits from this unprecedented price rally.

Instead, roughly 77% of America's tin supply was imported from foreign countries – Indonesia (24%), Malaysia (21%), Peru (20%), and Bolivia (17%) were the top suppliers of tin to the U.S. during 2020. The balance of U.S. tin supply, roughly 18,000 metric tons, was the product of recycling.

"Tin has not been mined or smelted in the United States since 1993 and 1989, respectively," USGS inked in its Mineral Commodity Summaries 2021 publication.

This complete dependence on foreign sources for new supply, coupled with the alloying metal's importance to both manufacturing and defense, is the reason both the Pentagon and USGS consider tin critical to the United States.

The two best options for the U.S. to break its dependency on imports for this critical electronics metal is to develop some of the more than 100 tin occurrences identified across Alaska and recycle more tin from the thousands of metric tons of circuit boards discarded every month.

Alaska's gateway tech metal

Aside from the geopolitical factors that weigh on U.S. dependency on imports for other critical minerals and metals, the primary reason there are not any American tin mines is that deposits of this alloying metal are rare in the contiguous 48 states.

Alaska, on the other hand, hosts more than 100 known tin occurrences, making it the best place to establish a domestic source of this long-lived critical metal.

"Today, Alaskan tin deposits are known to be widespread, occurring from the central Alaska Range north to the Brooks Range and across Interior Alaska ... Southwest Alaska and the Seward Peninsula," according to Mineral Deposits of Alaska, a 1997 publication that compiles the work of nearly 50 geologists.

And when it comes to technology minerals exploration in Alaska, tin could be considered the gateway metal due to its direct affiliation with more than a dozen of the 35 metals deemed critical to the U.S.

Beryllium, bismuth, chromium, fluorspar, gallium, indium, manganese, niobium, platinum group metals, rare earth elements, scandium, strontium, tantalum, tungsten, and vanadium are among the critical metals and groups of elements associated with the placer and lode tin occurrences across the state.

Most of Alaska's tin occurrences are placer deposits of cassiterite, the primary tin mineral, found across the breadth of the Far North State. This follows a global trend – most of the world's production comes from alluvial deposits, rather than the hardrock sources that provide ore for large-scale production of most metals and minerals.

"Placer deposits have traditionally been an important source of tin; in 2012, they accounted for about 70% of the world output of cassiterite concentrates," USGS penned in its 2018 critical minerals report.

There are a couple of advantages that make placer deposits an intriguing source of tin – Mother Nature has completed the first stage of mineral processing – eroding cassiterite from the hard rock sources and concentrating the tin mineral in deposits that can be mined with simple gravity recovery systems – and these rich sources of Alaska tin are almost always associated with an array of other metals critical to the United States.

Interior Alaska placer tin

One of the most intriguing places in Alaska to explore for critical minerals-enriched placer tin deposits is a 200-mile-long area in the Interior region of the state just north of the Yukon River that also happens to be prime hunting ground for rare earths.

Ray Mountains, which is about 40 miles north of the community of Tanana, is an area rich in placer tin, rare earths, and other critical minerals.

Ucore Rare Metals, who staked claims over much of this placer potential about a decade ago, carried out preliminary work to test the viability of mining the critical minerals in the alluvial deposits at Ray Mountain.

Concentrates from gravity separation of placer samples collected in 2014 returned up to 50% tin; 10% rare earths; and 0.01 to 1% tungsten, tantalum, and niobium.

Ucore, which is focused on a mine at its Bokan Mountain rare earth deposit and associated REE separation plant in Southeast Alaska, has not carried out any recent work in the Ray Mountains.

Gold-rich Alaska mining districts on the south side of the Yukon River also happen to be enriched with tin and associated critical minerals.

The best known of these tin- and gold-rich regions of Interior Alaska is the 12-mile-long Tofty tin belt in the Manley Hot Springs district about 90 miles northwest of Fairbanks.

"Gold mining in the district developed rapidly, and as the productive area in the vicinity of Tofty increased it was found that tin and gold were generally associated and that the richer concentrations of the two minerals were generally coincident," Henry Eakin wrote in a 1914 report, Tin Mining in Alaska.

This coincidence was oft a burden for early placer gold miners due the cassiterite, a relatively heavy mineral, plugging up sluice boxes and rendering them ineffective in recovering gold.

These miners, however, soon decided to try to cash in on the tin mineral piling up on their claims.

In 1911, about 1,200 lb of tin concentrates accumulated from cleaning out the sluice boxes were shipped to Singapore for processing.

"The ore was found to be of high quality, and the returns from the small shipment directed attention for the first time to the possible value of tin as a by-product," Eakin penned.

And in 1914, roughly 48 tons of cassiterite were shipped from the gold mines in the Hot Springs district.

Over the years since, various miners have recovered cassiterite as a by-product of gold mining.

While a search for the lode source of the Tofty Tin Belt placers did not turn up appreciable amounts of cassiterite, samples collected by the Alaska Division of Geological and Geophysical Surveys did find intriguing quantities of many other minerals deemed critical to the U.S.

Bismuth, chromium, gallium, manganese, niobium, rare earth elements, scandium, strontium, tantalum, and vanadium have been identified in samples collected from the Manley Hot Springs district.

About 200 miles east of Tofty and near another Interior Alaska hot springs, placer gold miners ran into similar problems of abundant tin plugging their sluice boxes while trying to recovery gold from Boulder Creek in the Circle Mining District.

While there has been no systematic testing of the placer tin content, a miner attempting to recover the gold in a particularly tin-enriched portion of Boulder Creek estimated the gravel contained more than 2 lb of cassiterite per yard.

An investigation by James Barker, a geologist that carried out extensive exploration of Alaska's critical minerals potential for the U.S. Bureau of Mines, indicates that the lode source of this tin mineralization is close.

"Cassiterite occurs as fresh unweathered crystals up to 3/8 of an inch long, some of which are attached to gangue rock," he wrote in a 1979 report. "Tin is particularly concentrated in the coarser size fractions. The gold is also quite fresh, occurring primarily as thin irregular flakes. The balance of the concentrate consists of rounded nuggets of hematite, magnetite, and scheelite."

Scheelite is a mineral of tungsten, which the USGS also considers critical.

One sample of fresh granite collected by Barker near Boulder Creek returned 20 parts per million tin and 22 ppm tungsten. The sample also contained gold and molybdenum.

Tin and tungsten have been found in many of the other creeks in the Circle Mining District – Bedrock, Deadwood, Independence and Half Dollar, to name a few.

The Lime Peak and Mount Prindle areas to the west of the Circle Hot Springs granitic intrusive feeding these creeks also has tin, tungsten, and rare earth mineralization.

Tin City and beyond

Any mining company looking for rich sources of tin in Alaska would be remiss if it overlooked a place called Tin City.

Located on the western tip of the Seward Peninsula, Tin City was established in 1904 by Nome Gold Rush miners who found rich deposits of cassiterite in Cape Creek about 90 miles northwest of Nome.

Placer mining of Cape Creek, which drains the mountain rising to the northwest of Tin City, produced an estimated 3.3 million pounds of tin, according to the USGS. The largest known chunk of cassiterite recovered during placer mining of Cape Creek weighed 142 lb.

While Tin City is more of a forgotten outpost than the metropolitan that its name suggests, the streams in the area and the highlands feeding those streams still hold rich stores of the critical metal for which the ghost town derived its name.

"One of the few primary hard-rock tin deposits in the United States is the Lost River tin-tungsten-fluorine deposit in the Seward Peninsula, Alaska," the USGS wrote in its 2018 critical minerals report.

Kougarok, located about 90 miles east of Tin City, is another promising lode tin deposit on the Seward Peninsula.

Work in the 1980s estimated a portion of the tin-bearing granites there hosts some 6 million lb of tin in 240,000 tons of historical resource averaging 1.3% tin. Some of the cassiterite deposits at Kougarok also host considerable amounts of critical metals beryllium, tungsten, fluorspar, niobium, and tantalum.

When it comes to hardrock sources of tin in Alaska, one of the more promising areas lies alongside the Parks Highway about midway between Fairbanks and Anchorage.

One such prospect, Coal Creek, was discovered by Charles Hawley in 1972 and explored by Houston Oil and Minerals in the 1980s.

After drilling 42 holes, Houston Oil estimated the Coal Creek deposit contained roughly 4.8 million metric tons averaging 0.27% tin.

While the resource does not meet the rigor of current reporting standards, sampling of core stored at the Alaska Geologic Materials Center in Anchorage and four holes drilled in 2006 confirms the tin-silver potential of this easily accessible property.

Highlights from the drilling include: 9.4 meters averaging 0.41% tin, 18.21 grams per metric ton silver and 0.81% zinc; and 9.3 meters averaging 0.45% tin, 11.95 g/t silver, and 0.29% zinc.

Lubor Ferenc; Wikimedia Commons

A pair of 10th century BC bronze swords found in Switzerland. The first civilizations to master the ability to alloy tin and copper had a strategic advantage over their counterparts.

Australia-based Discovery Africa Ltd. announced early in 2021 that it had staked claims over the Coal Creek discovery and other tin, silver, copper, and gold occurrences in the area.

The Aussie exploration company said it will prioritize its on-going exploration at Chulitna and is working toward identifying and reviewing other new projects, with a focus on Alaska.

At least four other hardrock tin prospects associated with other critical minerals – Sleitat, Bismarck Creek, Win, and Won – have been discovered in the Kuskokwim Mountains of Southwest Alaska.

So, while the Lower 48 states may not hold much promise for the tin needed for cans and robots alike, Alaska is heavily enriched with this alloying metal that has been critical to human progress for more than 5,500 years.

And, where you find tin in Alaska, a suite of other critical minerals is close by.

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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