4. Leases

Solitario leased one facility, its Wheat Ridge, Colorado office, that had a term of more than one year (the “WR Lease”). The WR Lease was classified as an operating lease which terminated on February 28, 2026. There is no remaining lease asset or lease liability related to the WR Lease at March 31, 2026. At December 31, 2025, the right-of-use office lease asset for the WR Lease was classified as other long-term assets and the related liability as current operating lease liabilities in the condensed consolidated balance sheet. The amortization of right-of-use lease asset expense was recognized over the lease term, with variable lease payments recognized in the period those payments are incurred.

During the three months ended March 31, 2026 and 2025, cash lease payments of $7,000 and $11,000, respectively, were made on the WR Lease. During the three months ended March 31, 2026 and 2025, Solitario recognized $7,000 and $10,000, respectively, of non-cash amortization of right-of-use lease asset expense for the WR Lease included in general and administrative expense. These cash payments, less imputed interest for each period, reduced the related liability on the WR Lease. The discount rate within the WR Lease was not determinable and Solitario applied a discount rate of 7% based upon Solitario’s estimate of its cost of capital to determine the asset and liability upon the extension of the WR lease during 2023.