Material Modification to Rights of Security Holders. The information set forth in the Introductory Note and Items 2.01, 3.01, 5.01, and 5.03 of this Current Report on Form 8-K is incorporated herein by reference.

Changes in Control of Registrant. The information set forth in the Introductory Note and Items 2.01, 5.02, and 5.03 of this Current Report on Form 8-K is incorporated herein by reference. As a result of the consummation of the Merger, a change of control of the Company occurred, and the Company became a direct, wholly owned subsidiary of Goldgroup.

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing. On the Closing Date, in connection with the consummation of the Merger, the Company notified NYSE American LLC (the “NYSE American”) that the Merger had been consummated and requested that the trading of its Common Stock on the NYSE American be suspended and that the listing of its Common Stock on the NYSE American be withdrawn. In addition, the Company requested that the NYSE American file wi…

Completion of Acquisition or Disposition of Assets. On the Closing Date, the Merger was consummated. Pursuant to the Arrangement Agreement, at the effective time of the Merger (the “Effective Time”), each outstanding share of common stock of the Company, par value $0.001 per share (“Company Stock”), was converted into the right to receive 1.4476 common shares of Goldgroup post-Merger (“Resulting Issuer Shares”) (adjusted to 0.3619 Resulting Issuer Shares as a result of a four-for-one share co…

Director — Allen Palmiere, Peter Gianulis, Lila Manassa Murphy and Ron Little: Departures were in connection with the Merger and not due to any disagreement.

Other Events As previously announced, on January 25, 2026, Gold Resource Corporation (the “Company”) entered into an Arrangement Agreement and Plan of Merger, as amended by that certain First Amendment to Arrangement Agreement dated May 15, 2026 (the “Arrangement Agreement”), with Goldgroup Mining Inc., a corporation incorporated under the laws of the province of British Columbia (“Goldgroup”), and Goldgroup Merger Sub Inc., a Colorado corporation and direct, wholly owned subsidiary of Goldgr…

Entry into a Material Definitive Agreement On May 15, 2026, Gold Resource Corporation (the “Company”), Goldgroup Mining Inc., a corporation incorporated under the laws of the Province of British Columbia (“Goldgroup”), and Goldgroup Merger Sub Inc., a Colorado corporation and direct subsidiary of Goldgroup (“Purchaser Sub”), entered into an amendment (the “Amendment”) to the previously announced Arrangement Agreement and Plan of Merger, dated January 25, 2026, by and among the parties (the “A…

Results of Operations and Financial Condition On May 7, 2026, Gold Resource Corporation (the “Company”) issued a news release reporting its production and unaudited financial results for the three months ending March 31, 2026. A copy of the news release is attached as Exhibit 99.1 to this report. In accordance with General Instruction B.2 of Form 8-K, the information in this Item 2.02, including Exhibit 99.1, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Excha…

Results of Operations and Financial Condition On March 18, 2026, Gold Resource Corporation (the “Company”) issued a news release reporting its production and unaudited financial results for the year ending December 31, 2025. A copy of the news release is attached as Exhibit 99.1 to this report. In accordance with General Instruction B.2 of Form 8-K, the information in this Item 2.02, including Exhibit 99.1, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchang…

Entry into a Material Definitive Agreement Arrangement Agreement and Plan of Merger On January 25, 2026, Gold Resource Corporation (the “Company”) entered into an Arrangement Agreement and Plan of Merger (the “Arrangement Agreement”) with Goldgroup Mining Inc., a corporation incorporated under the laws of the Province of British Columbia (“Goldgroup”), and Goldgroup Merger Sub Inc., a Colorado corporation and direct subsidiary of Goldgroup (“Purchaser Sub”). The Arrangement Agreement provides…

Results of Operations and Financial Condition. ​ On January 20, 2026, Gold Resource Corporation (the “Company”) issued a press release reporting its preliminary production results for the three and twelve months ended December 31, 2025 (the “Press Release”). A copy of the Press Release is attached as Exhibit 99.1 to this report. ​ In accordance with General Instruction B.2 of Form 8-K, the information in this Item 2.02, including Exhibit 99.1, shall not be deemed to be “filed” for purposes of…

Results of Operations and Financial Condition On November 4, 2025, Gold Resource Corporation (the “Company”) issued a news release reporting its production and unaudited financial results for the third quarter of 2025. A copy of the news release is attached as Exhibit 99.1 to this report. In accordance with General Instruction B.2 of Form 8-K, the information in this Item 2.02, including Exhibit 99.1, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act…

Entry into a Material Definitive Agreement On September 2, 2025, Gold Resource Corporation (the “Company”) entered into a securities purchase agreement (the “SPA”) with certain investors providing for the purchase and sale of up to 25,315,960 shares of its common stock at a price of $0.45 per share (the “Shares”) in a registered direct offering, resulting in estimated total gross proceeds to the Company of approximately $11.4 million (the “Offering”). The Offering closed on September 8, 2025.…

Results of Operations and Financial Condition On August 5, 2025, Gold Resource Corporation (“the Company”) issued a news release reporting its production and unaudited financial results for the second quarter of 2025. A copy of the news release is attached as Exhibit 99.1 to this report. In accordance with General Instruction B.2 of Form 8-K, the information in this Item 2.02, including Exhibit 99.1, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act o…

Entry into a Material Definitive Agreement The information set forth in

Unregistered Sales of Equity Securities The disclosure set forth in

Entry into a Material Definitive Agreement On June 26, 2025, Gold Resource Corporation (the “ Company ”) and its subsidiary Don David Gold Mexico S.A. de C.V. (“ DDGM ”) entered into a loan agreement (the “ Loan ”) with Francisco Javier Reyes de la Campa and Jaluca Limited (collectively, the “ Lender ”), whereby the Lender provided the Company with a loan in the principal amount of $6.28 million (the “ Principal Amount ”). The Loan bears an accrued interest at a per annum rate equal to the su…

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant ​ The disclosure set forth in

Director, Audit Committee Member, Compensation Committee Member — Peter Gianulis: Peter Gianulis was appointed as a director and committee member of Gold Resource Corporation.

Results of Operations and Financial Condition On May 12, 2025, Gold Resource Corporation (“the Company”) issued a news release reporting its production and unaudited financial results for the first quarter of 2025. A copy of the news release is attached as Exhibit 99.1 to this report. In accordance with General Instruction B.2 of Form 8-K, the information in this Item 2.02, including Exhibit 99.1, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1…

Chief Operating Officer — Alberto Reyes: Alberto Reyes is no longer employed as the Chief Operating Officer of Gold Resource Corporation.

Results of Operations and Financial Condition. ​ On April 8, 2025, Gold Resource Corporation (“the Company”) issued a news release reporting its production and financial results for the year ended 2024. A copy of the news release is attached as Exhibit 99.1 to this report. ​ In accordance with General Instruction B.2 of Form 8-K, the information in this Item 2.02, including Exhibit 99.1, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as am…

Non-Reliance on Previously Issued Financial Statements or a Related Audit Report of Completed Interim Review During the preparation of consolidated financial statements for the year ended December 31, 2024 of Gold Resource Corporation (the “Company”), management of the Company identified that liabilities related to the Company’s Back Forty Advance Exploration Project with respect to the carried over Gold and Silver Stream Agreements with Osisko Bermuda Limited (the “streaming liabilities”) we…

Entry into a Material Definitive Agreement On January 6, 2025 , Gold Resource Corporation (the “Company”) entered into securities purchase agreements with certain investors providing for the purchase and sale of up to 15,625,000 shares of its common stock at a price of $0.16 per share (the “Shares”) in a registered direct offering (the “Offering”). The Offering is expected to close on or about January 17 , 2025, subject to the satisfaction of customary closing conditions. The Shares will be s…

Results of Operations and Financial Condition. ​ On November 5, 2024, Gold Resource Corporation (“the Company”) issued a news release reporting its production and unaudited financial results for the third quarter of 2024. A copy of the news release is attached as Exhibit 99.1 to this report. ​ In accordance with General Instruction B.2 of Form 8-K, the information in this Item 2.02, including Exhibit 99.1, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange…