Critical materials explorer samples historical adits at high-grade rare earth project in SW Montana.

A fall program of underground exploration and sampling by US Critical Materials Corp. further confirms the idea that Sheep Creek is one of the highest-grade rare earth discoveries in the United States and supports the need for drilling to fully understand the scope of critical minerals mineralization at this project in southwestern Montana.

High-grade rare earths were found at Sheep Creek during niobium exploration in the late 1950s and early 60s. At that time, however, there were no uses for this enigmatic group of elements that are now critical to modern technologies. Instead, Continental Columbium Company, which carried out the historical exploration, was interested in the niobium found alongside the rare earths.

To gain a better understanding of the niobium potential at Sheep Creek, Continental dug three adits to trace the mineralization seen on surface.

Taking advantage of the potential to gain an underground view of the geology and mineralization at Sheep Creek, US Critical Materials opened up and sampled two of the adits.

This sampling has confirmed that the high-grade rare earths found on the surface continues underground. Samples of the critical minerals enriched carbonatite in the underground workings contain as much as 17% rare earths, including high grades of the neodymium and praseodymium that are in high demand due to their use in the powerful permanent magnets that go into electric vehicle motors, wind turbines, and a wide range of consumer electronics.

"These initial underground findings further support the potential for Sheep Creek to become a truly unique and valuable asset within the U.S.," said US Critical Materials President James Hedrick.

So far, US Critical Materials has identified 13 of the 50 minerals and metals critical to the U.S. – nine rare earths, gallium, niobium, scandium, and yttrium.

Heading underground

Much of the 2022 fall program at Sheep Creek focused on sampling two 1950s-era adits located about 2,000 meters, or more than a mile, apart.

Adit No. 1, found near the northwest end of the Sheep Creek property, follows a one- to three-foot thick vein of critical mineral-enriched carbonatite, a carbon-rich igneous rock that often hosts rare earth mineralization, for 270 meters underground.

Last year, a US Critical Materials geologist collected a grab sample of the vertical vein of carbonatite from surface about 50 feet above Adit No. 1 that contains 16.44% total rare earth oxides, including 1.66% neodymium oxide and 0.63% praseodymium oxide.

The rare earths sampled on surface were associated with a mineral known as ancylite, which has been identified throughout the carbonatite traced in Adit No. 1.

Even higher-grade rare earths were collected from surface samples associated with Adit No. 3, which lies about 2,000 meters southeast of Adit No. 1.

A grab sample of ancylite-bearing carbonatite collected from a 2021 trench above Adit No. 3 contains 17.05% total rare earth oxides, including 1.57% neodymium oxide and 0.62% praseodymium oxide.

Another sample of carbonatite from the mine dump at Adit No. 3, a pile of rocks excavated while digging underground, averaged 7.26% rare earth oxides, including 0.84% neodymium oxide and 0.31% praseodymium oxide.

An X-ray fluorescence (XRF) scan of the carbonatite in the walls of Adit No. 3 showed 8.7% cerium, 6.9% lanthanum, and 2.8% strontium – three rare earths common in ancylite.

Definitive assays from the 2022 sampling of both adits are pending analysis by Activation Laboratories in Ontario, Canada.

More than a dozen surface samples collected between adits No. 1 and No. 3 have also turned up high-grade rare earths, and the trend continues at least 1,500 meters southeast of Adit No. 3.

"During my time with the US Geological Survey, as the rare earths analyst, I had the opportunity to review the majority of the rare earth projects in the U.S.," said Hedrick. "In my professional opinion, there are very few assets in the U.S. that have the potential which continues to be uncovered at Sheep Creek."

Preparing for drilling

Given the vast rare earths potential identified with both underground and surface sampling and mapping, US Critical Materials is looking forward to an inaugural drill program at Sheep Creek in 2023.

To gain the federal authorizations for drilling and other exploration, the company is preparing a plan of operation to submit to the U.S. Forest Service.

The 2022 program and expanded exploration at Sheep Creek in 2023 is being funded by US Critical Metals, which entered into an agreement to earn up to a 75% interest in Sheep Creek and the Lemhi Pass rare earths project just across the border in Idaho by investing as much as US$10 million over three phases.

To earn an initial 25%, US Critical Metals paid U.S. Critical Materials US$300,000 and has agreed to invest an initial US$1.5 million in exploration over the first 16 months.

This initial earn-in helped fund the opening of the adits, as well as the 2022 sampling and mapping that affirmed the high-grade rare earths at Sheep Creek.

US Critical Materials Corp.

Pink ancylite mineralization in a three-foot thick carbonatite vein in Adit No. 3 on US Critical Materials' Sheep Creek project.

"These findings continue to support our business model of identifying teams with proven expertise in specific commodities and providing the capital required to advance those projects in a timely and impactful manner," said US Critical Metals CEO Darren Collins. "It is a pleasure to continue to work with Jim and his team and we look forward to further results from Sheep Creek."

Once the spending requirements for the initial earn-in are met, US Critical Metals will have the option to increase its stake to 50% by paying US$200,000 in cash and investing an additional US$3 million into exploration over 40 months.

To earn a 75% interest in Sheep Creek and Lemhi Pass, US Critical Metals would fund an additional US$5 million for a third phase of exploration and other work toward advancing development at the Montana and Idaho rare earths projects over 64 months.