| ● | Slag Sales – We recorded $0.2 million in revenue related to the gold and silver in slag that was sold to a refiner in the United States in the three months ended September 30, 2023. There were no slag sales in the three months ended September 30, 2022. |
Cost of metals sold. For the three months ended September 30, 2023 and 2022, we recorded $3.3 million and $4.4 million of cost of metals sold, respectively. Lower costs in 2023 compared to 2022 were due primarily to lower mining costs as mining operations at Rodeo concluded at the end of June 2023.
Exploration expense. Our exploration expense, including property holding costs and allocated administrative expenses, totaled $0.7 million and $2.4 million for the three months ended September 30, 2023 and 2022, respectively. The lower exploration expense for 2023 is primarily related to the absence of costs related to increase the capacity of the tailings facility at Velardeña incurred in the three months ended September 30, 2022 which were not incurred during the three months ended September 30, 2023.
Velardeña care and maintenance costs. We recorded $0.3 million and $0.4 million for the three-month periods ended September 30, 2023 and 2022, respectively, for expenses related to care and maintenance at our Velardeña Properties as the result of the suspension of mining and processing activities in November 2015.
El Quevar project expense. We incurred $0.1 million and $0.2 million for the three-month periods ended September 30, 2023 and 2022, respectively, related to holding and evaluation costs for the Yaxtché deposit at our El Quevar project in Argentina. During the three months ended September 30, 2023 and 2022, approximately $0.0 million and $0.1 million, respectively, of costs actually incurred were offset by reimbursements from Barrick as discussed above.
Administrative expense. Administrative expenses totaled $1.1 million and $0.9 million for the three months ended September 30, 2023 and 2022, respectively. Administrative expenses, including costs associated with being a public company, are incurred primarily by our corporate activities in support of the Rodeo Property, Velardeña Properties, El Quevar project and our exploration portfolio.
Stock-based compensation. During the three months ended September 30, 2023 and 2022, we incurred approximately $0.1 million and $0.2 million, respectively, of expense related to stock-based compensation. Stock-based compensation varies from period to period depending on the number and timing of shares granted, the type of grant, the market value of the shares on the date of grant and other variables.
Reclamation and accretion expense. During each of the three months ended September 30, 2023 and 2022, we incurred approximately $0.1 million of reclamation expense related to the accretion of an asset retirement obligation at the Velardeña Properties and environmental liabilities associated with the Rodeo operation.
Other operating income, net. We recorded $0.5 million of other operating income for the three months ended September 30, 2023 primarily related to the sale of non-core assets. For the three months ended September 30, 2022, we recorded $0.4 million of other operating income primarily related to the amortization of deferred income related to the option agreement for the sale of the Santa Maria property described in our 10-K report for the year ended December 31, 2022.
Depreciation, depletion and amortization. During each of the three months ended September 30, 2023 and 2022, we incurred depreciation, depletion and amortization expense of approximately $0.1 million.
Interest and other expense, net. We recorded a nominal amount of interest and other expense, net for each of the three months ended September 30, 2023 and 2022.
Litigation settlement expense. During the three months ended September 30, 2023, we recorded approximately $0.3 million to settle the Unifin matter discussed below in item 1 of Part II. During the three months ended September 30, 2022, we recorded approximately $0.0 million.
Gain (loss) on foreign currency losses. During the three months ended September 30, 2023, we recorded a nominal amount of foreign exchange gains. During the three months ended September 30, 2022, we recorded $0.2 million of foreign exchange gains. Foreign currency gains and losses are primarily related to the effect of currency fluctuations on monetary transactions incurred by our foreign subsidiaries that are denominated in currencies other than U.S. dollars.