Wartime Tantalum: How the Black Hills Supplied the US in the 1940s

In 1942, the United States government sent geologists into the Black Hills to map pegmatites. It was not an academic exercise. The country was at war, imported supplies of specialty metals were uncertain, and tantalum, tin, and lithium minerals were on the list of materials the war effort could not do without. For a few years, one of the answers to a national supply problem ran through Lawrence, Pennington, and Custer counties in South Dakota.

This article covers what wartime tantalum supply from the Black Hills actually looked like, which districts were involved, and why the same questions the government was asking in the 1940s are being asked again in the 2020s.

Why Did Tantalum Become a Strategic Metal in the 1940s?

Tantalum became a strategic metal because wartime equipment needed it and the United States had no secure domestic supply. Tantalum is dense, extremely corrosion resistant, and stable at high temperatures. By the early 1940s it was being used in electron tubes and related components for radio and electronic equipment, in corrosion-proof equipment for chemical processing, and in surgical skull plates for wounded soldiers.

The US industrial tantalum business of the era was led by Fansteel Metallurgical Corporation of Illinois, which had pioneered industrial applications of the metal from the 1910s onward and expanded sharply during the war as military demand for electrical components grew [6]. Feeding that industry required ore, and the principal ore mineral of tantalum, columbite-tantalite, came mostly from overseas. Wartime shipping risk made that dependence a problem, and the government responded the way it did for dozens of strategic materials: it mapped domestic deposits, prioritized their development, and bought what they produced.

What Did the Federal Government Do in the Black Hills?

The federal government sent its geologists. The U.S. Geological Survey had documented tin, tungsten, and tantalum deposits in South Dakota as far back as 1908 [1], and in 1941, with war approaching, it published a fresh assessment of the tin-bearing pegmatites of the Tinton District in Lawrence County [2].

Then came the systematic campaign. From 1942 to 1945, USGS field teams worked across the Black Hills producing descriptions, maps, and diagrams of pegmatite deposits of mica, beryl, lithium, tantalum, tin, and feldspar. The results were later compiled as USGS Professional Paper 247, one of the foundational documents of Black Hills pegmatite geology [3]. The federal government does not deploy geologists for four years into districts it considers unimportant. The wartime mapping is direct evidence of how seriously Washington took the Black Hills as a domestic source of strategic pegmatite minerals.

Which Black Hills Districts Supplied Strategic Minerals?

Two areas mattered most. In the southern Black Hills, the pegmatite fields around Keystone, Custer, and Hill City produced columbite-tantalite largely as a byproduct of mining mica, feldspar, beryl, and lithium minerals. In the northern Black Hills, the Tinton District in Lawrence County hosted the region's tin-bearing pegmatites, with tantalum and lithium minerals in the same system.

The Tinton District had been a producer since the early 1900s, with approximately 105,000 pounds of tin produced between 1903 and 1927 from pegmatites clustered around the district core [2]. The district's pegmatites carried more than tin: the same bodies host tantalum at Volney, tin at Volney, and lithium at Volney in the mineral assemblage that defines LCT pegmatite systems.

Historical production note: Production figures cited in this article are historical, drawn from government publications of the period. They have not been verified by a qualified person, are not compliant with NI 43-101, and should not be relied upon as indicative of current or future mineralization or production.

Black Hills Strategic Minerals, 1903 to 1959

What Happened to US Tantalum Production After the War?

It ran for another decade and a half, then stopped. Government demand did not end in 1945. Cold War stockpiling and the Korean War kept strategic minerals programs alive into the 1950s, with the government paying premium prices for columbium and tantalum concentrates and funding exploration through the Defense Minerals Exploration Administration [4]. Under those conditions, 1954 was a record year: South Dakota led the nation, with twelve Black Hills pegmatite mines producing columbite-tantalite, principally as a byproduct of mica, feldspar, and beryl mining [4].

When the government programs wound down, the economics went with them. US deposits were smaller and lower grade than the large pegmatite systems being developed overseas, and tantalum has not been mined in the United States since 1959 [5].

How Does the 1940s Story Connect to Critical Mineral Security Today?

The dependence the government scrambled to manage in 1942 exists today in a stronger form. The U.S. Geological Survey reports that US net import reliance for tantalum was 100% in every year from 2021 through 2025, with estimated apparent consumption of 890 tonnes of tantalum in 2025 [5]. World mine production is concentrated in central Africa, led by the Democratic Republic of the Congo, and nearly half of US imports of tantalum metal and powder over 2021 through 2024 came from China [5]. Tantalum appears on the 2025 US List of Critical Minerals, and its modern uses read like an upgraded version of the wartime list: capacitors in essentially every electronic device, defense electronics, aerospace superalloys, and semiconductor manufacturing equipment [5]. A fuller breakdown is in our guide to the US tantalum supply chain.

US Tantalum at a Glance (USGS, 2026)

Source: U.S. Geological Survey, Mineral Commodity Summaries 2026 [5].

There is one important difference between then and now. In the 1940s it took a world war to force a national inventory of domestic mineral supply. Today, the US Critical Minerals List exists to identify those exposures in peacetime, and the districts the wartime geologists mapped are being examined again with modern tools. The Tinton District is among them. The Volney Project, held by Lion Rock Resources, sits within the district, and the Company's Phase 1 drill program confirmed lithium, tin, and tantalum in the same pegmatite systems the wartime programs worked. The ground the government mapped in 1942 is, once again, ground the country has a reason to understand. For the geological background, see our explainer on what a pegmatite is and our overview of Black Hills mining history.

Policy note: No US government program, funding, incentive, or policy referenced in this article applies to, benefits, or is accessible to Lion Rock Resources or the Volney Project. The wartime and postwar government programs described here ended decades ago and are discussed for historical context only.

Frequently Asked Questions

Did the Black Hills ever produce tantalum?

Yes. Black Hills pegmatites produced columbite-tantalite, the principal ore mineral of tantalum, through the first half of the 20th century, mostly as a byproduct of mining mica, feldspar, beryl, and lithium minerals. In 1954, South Dakota was the leading US producer of columbium-tantalum concentrates. These figures are historical and have not been verified under NI 43-101.

Does the United States produce tantalum today?

No. Tantalum has not been mined in the United States since 1959. The U.S. Geological Survey reports that the United States has been 100% net import reliant on tantalum in every year from 2021 through 2025, and tantalum is on the 2025 US List of Critical Minerals.

Related Reading

US Tantalum Supply Chain: Closing the 100% Import Gap

The Black Hills: America's Overlooked Mining Powerhouse

What Is a Pegmatite?

Tin Price Forecast

Disclaimer

This article is provided for general educational purposes only and does not constitute investment advice or an offer to buy or sell securities. Historical production figures are drawn from historical government publications, have not been verified by a qualified person, and are not compliant with NI 43-101. Third-party statistics are drawn from the sources cited and have not been independently verified by Lion Rock Resources. Past production is not indicative of current or future mineralization, production, or economic viability.

References

[1] Hess, F.L., 1908. Tin, Tungsten, and Tantalum Deposits of South Dakota. U.S. Geological Survey Bulletin 380-D. https://pubs.usgs.gov/bul/0380d/report.pdf

[2] Smith, W.C. and Page, L.R., 1941. Tin-Bearing Pegmatites of the Tinton District, Lawrence County, South Dakota, a Preliminary Report. U.S. Geological Survey Bulletin 922-T. https://www.usgs.gov/publications/tin-bearing-pegmatites-tinton-district-lawrence-county-south-dakota-a-preliminary

[3] Page, L.R., et al., 1953. Pegmatite Investigations 1942-45, Black Hills, South Dakota. U.S. Geological Survey Professional Paper 247. https://doi.org/10.3133/pp247

[4] US Bureau of Mines, 1954. Minerals Yearbook 1954, Columbium and Tantalum chapter. https://search.library.wisc.edu/digital/APPWSVFNGRNNLT8E/text/A6UMBUOG6LMP3K8I

[5] U.S. Geological Survey, 2026. Mineral Commodity Summaries 2026: Tantalum. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-tantalum.pdf

[6] Encyclopedia of Chicago. Fansteel Inc. http://www.encyclopedia.chicagohistory.org/pages/2658.html