Thunder Mountain Gold Expands South Mountain Project Resources

Thunder Mountain Gold, Inc. has announced positive results from its 2026 exploration program at the South Mountain Project in southern Idaho. The company’s efforts have expanded the known resource potential and identified new targets, positioning the project as a significant growth asset in the U.S. critical and precious metals sector.

The exploration program, which included 8,500 feet of diamond core drilling, focused on expanding the existing carbonate replacement deposit (CRD) massive sulfide resource while also testing district-scale copper-gold porphyry targets. Four drill holes tested the up-dip extension of the DMEA massive sulfide "chimney" and intersected intense skarn alteration containing copper, zinc, and lead sulfides. Initial assay results from three of these holes confirmed strong enrichment in silver and gold within the massive sulfides, with one hole returning 22.47 meters grading 86 g/t silver.

Step-out drilling of three holes at the Kentucky Ridge target demonstrated approximately 80 meters of down-plunge continuity. These holes intersected a surface gossan grading 7.6 meters at 125 g/t silver, 1.2% lead, and 1.7% zinc in a channel sample. Visual review of the drill intercepts noted approximately 15 meters of intense gossan and a deeper intersection of intensely silicified, pyrrhotite-sphalerite (Zn sulfide) mineralization. The mineralized zone remains open at depth, suggesting potential for further exploration.

Three additional holes targeted the Laxey Marble, including one hole testing a historic induced-polarization geophysical anomaly further northwest of the massive sulfide resource area. Two additional holes, at the southeast end of the trend, tested the Laxey Marble approximately 400 meters to the southeast of the resource area. These holes intersected intensely sericitic, pyrite-rich brecciated schist and marble with localized skarn alteration. Assays for these samples are pending.

Eric T. Jones, President and Chief Executive Officer of Thunder Mountain Gold, commented, "This program has accomplished our goal of demonstrating significant near-resource expansion potential while opening the door to larger district-scale discovery opportunities. The breadth of alteration and sulfide mineralization encountered in these first drill holes is a significant technical success for the company."

The Big Grass Fire, which originated in Oregon and moved through Owyhee County and the South Mountain District in late July, did not result in any damage to company structures or equipment. The fire temporarily delayed exploration activities but did not have a material impact on the 2026 exploration drilling campaign.

Thunder Mountain Gold has advanced the South Mountain Mine project since 2007, investing approximately US$25 million to date. The company's expanded land position now totals approximately 13,061 acres, or roughly twenty square miles, following the purchase of 113 acres of private land contiguous with the main historic mine area, the staking of 423 mineral lode claims on adjoining BLM lands totaling approximately 8,200 acres, and a lease covering an additional 1,073 acres of private land in and around the project area.

The South Mountain Mine is a polymetallic development project containing high-grade silver, zinc, gold, copper, and lead mineralization on private land approximately 70 miles southwest of Boise, Idaho. The project includes a long history of mining, with more than 8,000 feet of historic underground workings and approximately 4,000 feet of rehabilitated MSHA-compliant underground development.