Thunder Mountain Gold names Osterberg exploration VP

Q: What options did THMG grant its new exploration chief?

The company granted 250,000 options to purchase up to 250,000 common shares at an exercise price of $0.75 per share. They vest immediately upon grant, subject to TSX Venture Exchange approval; the grant is effective October 1, 2026, and the options expire September 30, 2031.

Q: What makes up Thunder Mountain Gold’s South Mountain land position?

The approximately 13,061-acre land position includes a purchase of 113 acres contiguous with the historic mine area, 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.

The option grant carries a $0.75 exercise price and expires September 30, 2031, subject to TSX Venture Exchange approval.

Available on EDGAR 11/04/2026 - 03:20 PM EST Accepted by SEC EDGAR 11/04/2026 - 03:20 PM EST

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Form Type

8-K

Rhea-AI Filing Summary

Thunder Mountain Gold appointed Steven A. Osterberg, Ph.D., P.G., Q.P., as Senior Vice-President of Exploration effective September 8, 2026, and accepted Ron Espell’s resignation as Chief Operating Officer effective that date. The company granted 250,000 options to purchase up to 250,000 common shares at an exercise price of $0.75 per share. The options vest immediately upon grant, are subject to TSX Venture Exchange approval, and the grant is effective October 1, 2026, with an expiration date of September 30, 2031.

Osterberg will lead target generation, technical evaluation, drilling and resource-growth initiatives. The company describes South Mountain as a polymetallic project with approximately 13,061 acres and approximately US$25 million invested to date. It reports more than 8,000 feet of historic underground workings and approximately 4,000 feet of rehabilitated MSHA-compliant underground development.

8-K Event Classification

4 items: 3.02, 5.02, 8.01, 9.01

4 items

Item 3.02 Unregistered Sales of Equity Securities Securities

The company sold equity securities in a private placement or other unregistered transaction.

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers Governance

Key personnel changes including departures, elections, or appointments of directors and executive officers.

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, or exhibit attachments filed with this report.

Key Figures

Option grant: 250,000 options to purchase up to 250,000 common shares Exercise price: $0.75 per share Option term: Five years +4 more

7 metrics

Option grant 250,000 options to purchase up to 250,000 common shares Granted in connection with Osterberg’s appointment

Exercise price $0.75 per share Price for each option share

Option term Five years From the date of grant; effective October 1, 2026, with expiration on September 30, 2031

South Mountain land position Approximately 13,061 acres Company land position in and around the project

South Mountain investment to date Approximately US$25 million Company investment in the project

Historic underground workings More than 8,000 feet At the South Mountain project

Rehabilitated underground development Approximately 4,000 feet MSHA-compliant development at South Mountain

Key Terms

Qualified Person, S-K 1300, NI 43-101, restricted securities, +1 more

5 terms

Qualified Person technical

"a "Qualified Person" as defined by the U.S. S-K 1300 regulations"

A qualified person is someone with specialized knowledge, experience, and training in a particular field, allowing them to accurately assess and verify information or work. Their expertise helps ensure that reports, evaluations, or decisions are trustworthy and meet required standards. For investors, a qualified person provides confidence that the information they rely on is credible and properly validated.

S-K 1300 regulatory

"U.S. S-K 1300 regulations"

Regulation S-K Item 1300 is a U.S. securities disclosure rule that requires public companies to report how they manage cybersecurity risks and to promptly disclose material cyber incidents. Think of it as a requirement to tell investors both the company’s “cyber health” plan and any major break-ins, similar to a homeowner explaining their alarm system and alerting neighbors after a burglary. This helps investors assess operational risk and potential financial or reputational impact.

NI 43-101 regulatory

"National Instrument 43-101 standards"

A Canadian regulatory standard that sets the rules for how mining and exploration companies must report mineral resources and reserves, requiring technical reports prepared or signed off by an independent, certified expert. It matters to investors because it creates a consistent, transparent “inspection report” for mining projects, making it easier to compare prospects, judge the reliability of claims, and assess geological and financial risk before investing.

restricted securities regulatory

"issued as "restricted securities" (as defined in Rule 144"

Restricted securities are shares or other investment instruments that come with legal or contractual limits on when and how they can be sold, like stock given to founders or bought in a private offering. Think of them as assets in a locked box that can’t be freely traded until certain conditions — such as a waiting period, company registration, or specific approvals — are met. For investors this matters because restricted securities are less liquid and can affect timing, price, and perceived value when they eventually enter the market.

mineral lode claims technical

"423 mineral lode claims on adjoining BLM lands"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

Who is Thunder Mountain Gold’s new exploration chief?

Thunder Mountain Gold appointed Steven A. Osterberg, Ph.D., P.G., Q.P., as Senior Vice-President of Exploration effective September 8, 2026. He is a professional geologist and qualified person with more than 45 years in mining, spanning exploration, development, hydrogeology and permitting.

What options did THMG grant its new exploration chief?

The company granted 250,000 options to purchase up to 250,000 common shares at an exercise price of $0.75 per share. They vest immediately upon grant, subject to TSX Venture Exchange approval; the grant is effective October 1, 2026, and the options expire September 30, 2031.

What makes up Thunder Mountain Gold’s South Mountain land position?

The approximately 13,061-acre land position includes a purchase of 113 acres contiguous with the historic mine area, 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.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
___________________________

FORM 8-K

CURRENT REPORT
Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 8, 2026

THUNDER MOUNTAIN GOLD, INC.
(Exact name of registrant as specified in its charter)

Idaho	001-08429	91-1031075
(State or other jurisdiction	(Commission	(IRS Employer
of incorporation)	File Number)	Identification No.)

11770 W. President Drive, Ste. F
Boise, Idaho, United States 83713
(Address of principal executive offices) (ZIP Code)

Registrant’s telephone number, including area code: (208) 658-1037

11770 W. President Dr., Ste. F
Boise, Idaho, 83713 United States
(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(g) of the Act:

Title of each class	Trading Symbols	Name of each exchange on which registered
Common Stock, $0.001 par value	THMG	OTCQB

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b -2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

SECTION 3 - SECURITIES AND TRADING MARKETS

Item 3.02 Unregistered Sales of Equity Securities.

To the extent required by Item 3.02 of Form 8-K, the information set forth in Item 5.02 of this Current Report on Form 8-K is incorporated herein by reference. The transaction is relying on the exemption from registration provided by Section 4(a)(2) of the United States Securities Act of 1933, as amended (the "U.S. Securities Act") and applicable exemptions from state securities registration requirements.

SECTION 5 - CORPORATE GOVERNANCE AND MANAGEMENT

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

Resignation of Chief Operating Officer

Thunder Mountain Gold, Inc. (the "Company") accepted the resignation of Mr. Ron Espell as Chief Operating Officer of the Company effective September 8, 2026.

Appointment of Senior Vice-President of Exploration

Steven A. Osterberg, Ph.D., P.G., Q.P. (Qualified Person)

The Company engaged Dr. Steven A. Osterberg, age 65, as the Company's Senior Vice-President of Exploration effective September 8, 2026.

Dr. Osterberg will lead Thunder Mountain Gold's exploration strategy, including target generation, technical evaluation, drilling programs, and resource-growth initiatives across the Company's project portfolio. His appointment supports the Company's renewed focus on advancing the South Mountain Project in southern Idaho, an advanced-stage polymetallic asset with silver, zinc, gold, copper, and lead mineralization, as well as evaluating broader district-scale exploration opportunities.

Dr. Osterberg is a professional geologist and qualified person with over 45 years in mining, spanning exploration through development, hydrogeology, and permitting. Former VP Exploration and President/CEO at Timberline Resources, with extensive experience managing multidisciplinary teams and advancing projects through resource estimation, technical studies, and permitting. Senior author and qualified person contributor to multiple NI 43-101 and S-K 1300 technical disclosures.

From 2012 to August 2024, Dr. Osterberg held senior leadership positions with Timberline Resources Corporation. He previously served as its President and Chief Executive Officer before transitioning to Vice President of Exploration and director in October 2020. Since August 2024, Dr. Osterberg has worked as an independent consulting geologist and hydrogeologist through Osterberg Geoscience Services, LLC, providing geological and hydrogeological consulting services to mining clients. He previously also conducted an independent consulting practice through that firm from 2006 to 2009. Earlier in his career, he served as a Senior Geologist and Hydrogeologist with Knight Piesold, Ltd. from 1999 to 2001. Dr. Osterberg holds a Ph.D. from the University of Minnesota, a Master of Science from the University of Minnesota, Duluth, and a Bachelor of Science from the University of Wisconsin, Oshkosh.

The press release and this Current Report on Form 8-K do not constitute an offer to sell, or a solicitation of an offer to buy any security, and shall not constitute an offer, solicitation or sale in any jurisdiction in which such offering would be unlawful.

Compensation

In connection with Dr. Osterberg's appointment, the Company granted Dr. Osterberg 250,000 stock options (the "Options") under the Company's 2014 Stock Option Plan to purchase up to 250,000 shares of common stock of the Company (each, an "Option Share") at an exercise price of $0.75 per Option Share for a period of five years from the date of grant effective October 1, 2026 expiring on September 30, 2031, subject to the approval of the TSX Venture Exchange (the "Exchange".). The Options vest immediately upon grant.

All securities issued to Dr. Osterberg will be issued in reliance on the exemption from registration provided by Section 4(a)(2) of the U.S. Securities and applicable exemptions from state securities registration requirements, and will be issued as "restricted securities" (as defined in Rule 144 under the U.S. Securities Act). In addition, such securities will be subject to an Exchange four-month hold period.

No Family Relationships with Existing Directors or Executive Officers

Dr. Osterberg is not related to any existing director or executive officer of the Company, and, except as disclosed in this current report, the Company has neither nominated nor chosen any other person (whether related to Dr. Osterberg or otherwise) to become a director or executive officer of the Company.

No Related Party Transactions

There are no transactions involving the Company and Dr. Osterberg that are required to be reported pursuant to Item 404(a) of Regulation S-K. Dr. Osterberg has not been party to any transaction with the Company since the beginning of the Company's last fiscal year and is not party to any proposed transaction with the Company, involving an amount exceeding $120,000 and in which he had or will have a direct or indirect material interest.

No legal proceedings

Dr. Osterberg has not been involved in any legal proceedings required to be disclosed as enumerated in Item 401(f) of Regulation S-K that occurred during the past ten years.

SECTION 8 - OTHER EVENTS

Item 8.01 Other Events.

On September 8, 2026, the Company issued a news release disclosing the engagement of Dr. Steven Osterberg as Senior Vice-President of Exploration of the Company.

SECTION 9 - FINANCIAL STATEMENTS AND EXHIBITS

Item 9.01. Financial Statements and Exhibits.

99.1	News Release dated September 8, 2026 re: Thunder Mountain Gold Announces Key Leadership Addition Strengthening Exploration Team

104	Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

	THUNDER MOUNTAIN GOLD, INC.

DATE: November 4, 2026	By:	/s/ ERIC JONES
		Eric Jones
		President and Chief Executive Officer

	THUNDER MOUNTAIN GOLD INC.
TSX-V: THM OTCQB: THMG	11770 W. President Dr., Ste. F Boise, Idaho 83713 phone: (208) 658-1037

*NEWS RELEASE*

Thunder Mountain Gold Announces Key Leadership Addition
Strengthening Exploration Team

Boise, Idaho - September 8, 2026 - Thunder Mountain Gold, Inc. (OTCQB: THMG; TSX-V: THM) (the "Company" or "Thunder Mountain Gold") today announced the appointment of Dr. Steven Osterberg as Senior Vice President of Exploration, effective immediately. The Company also announced that Ron Espell has stepped down as Chief Operating Officer.

"We are pleased to welcome Steve to his new leadership role," said Eric T. Jones, President and Chief Executive Officer of Thunder Mountain Gold. "Steve's technical experience and exploration background will be important as we continue to advance South Mountain and pursue opportunities to expand the Company's mineral resource base. On behalf of the Board and the Company, I want to thank Ron Espell for his service as Chief Operating Officer. Ron contributed meaningful operational, environmental, and permitting insight during an important period for Thunder Mountain Gold, and we wish him continued success in his future endeavors."

Dr. Osterberg added, "I appreciate the opportunity to join Thunder Mountain in leading the exploration at South Mountain on a truly exciting project. The project is rare and compelling with district-scale potential for both new discoveries of silver-zinc massive sulfide mineralization, and for copper- gold. I look forward to building on the team's strong technical foundation towards discovery."

South Mountain Positioned as a U.S. Critical and Precious Metals Growth Asset

The South Mountain Mine is a polymetallic development project containing high-grade zinc, silver, gold, copper, and lead mineralization on private land approximately 70 miles southwest of Boise, Idaho. The project includes a long history of mining, more than 8,000 feet of historic underground workings, and approximately 4,000 feet of rehabilitated MSHA-compliant underground development. Thunder Mountain Gold has advanced the project since 2007 and invested 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.

Website:www.thundermountaingold.com
OTCQB: THMG | TSX-V: THM

This growing land package, combined with established infrastructure, historical production, a defined mineral resource, and multiple new exploration targets, positions South Mountain as a compelling U.S.-based critical and precious metals opportunity.

Technical Data in this Release

The technical information in this news release was reviewed and approved by Steven A. Osterberg, Ph.D., P.G., Q.P. consulting geologist, and is a "Qualified Person" as defined by the U.S. S-K 1300 regulations and National Instrument 43-101 standards.

Regarding Thunder Mountain Gold, Inc.

Thunder Mountain Gold Inc., founded in 1935, is a junior exploration company focused on advancing base and precious metals assets in the western United States. The Company's principal asset is the South Mountain Mine, a historic former Anaconda Copper Company development of zinc, silver, gold, lead, and copper located on private land in Owyhee County, Idaho. Thunder Mountain Gold also owns 100% of the Trout Creek Project, a gold exploration asset in Nevada adjacent to and surrounded by Nevada Gold Mines, a Barrick-Newmont joint venture. With a growing land position, established project infrastructure, and exposure to both critical and precious metals, Thunder Mountain Gold offers investors leverage to exploration success in premier U.S. mining jurisdictions. For more information, please visit the Company's website at www.Thundermountaingold.com, www.SEC.gov, and www.sedarplus.ca.

Cautionary Note to Investors

This news release is intended for release in the United States only. Neither the TSX Venture Exchange, the OTCQB, nor either of its Regulation Services Provider accepts responsibility for the adequacy or accuracy of this release.

For further information, please contact:

Thunder Mountain Gold, Inc.

Eric T. Jones

President and Chief Executive Officer

Eric@thundermountaingold.com

Office: (208) 658-1037

Source: View Original Filing on SEC EDGAR

Filing Exhibits & Attachments

6 documents

Press Releases

EX-99.1 EXHIBIT 99.1 8.6 KB