Oxide plant lease costs. We recorded $0.6 million of costs related to the oxide plant lease during the three-month period ended September 30, 2020. The costs consist primarily of reimbursable labor and utility costs which for accounting purposes are also included in revenue from the oxide plant lease. The Velardeña oxide plant lease was terminated in November 2020. We did not record any costs related to the oxide plant lease during the three-month period ended September 30, 2021.
Exploration expense. Our exploration expense, including property holding costs and allocated administrative expenses, totaled $2.1 million and $1.2 million for the three months ended September 30, 2021, and September 30, 2020, respectively. The higher exploration expense for 2021 is primarily related to increased exploration at our Velardeña Properties, Rodeo operation in Mexico and Sarita Este property in Argentina during the period.
Velardeña care and maintenance costs. We recorded $0.4 million and $0.2 million for the three-month periods ended September 30, 2021 and September 30, 2020, 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 $0.1 million for the three-month periods ended September 30, 2021, and September 30, 2020, 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, 2021 and September 30, 2020, approximately $0.2 million and $0.1 million of costs actually incurred were offset by reimbursements from Barrick, respectively as discussed above.
Administrative expense. Administrative expenses totaled $0.9 million for the three months ended September 30, 2021. 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. The $0.8 million of administrative expenses we incurred during the three months ended September 30, 2021, is comprised of $0.3 million of employee compensation and directors’ fees, $0.3 million of professional fees and $0.3 million of insurance, rents, travel expenses, utilities and other office costs. Administrative expenses totaled $0.9 million for the three months ended September 30, 2020. The $0.9 million of administrative expenses we incurred during the three months of 2020 is comprised of $0.2 million of employee compensation and directors’ fees, $0.4 million of professional fees and $0.3 million of insurance, rents, travel expenses, utilities and other office costs.
Stock based compensation. During each of the three-month periods ended September 30, 2021, and September 30, 2020 we incurred approximately $0.1 million 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. Stock based compensation was higher in the 2021 period due primarily to stock awards granted to executives and a consultant.
Reclamation and accretion expense. During each of the three months ended September 30, 2021, and September 30, 2020 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 (expense), net. We recorded $0.1 million of other operating income for the three months ended September 30, 2021, primarily related to the amortization of deferred income related to the option agreement for the sale of the Santa Maria property, as discussed above. We recorded a nominal amount of other operating expense for the three months ended September 30, 2020, primarily related to the sale of equipment in Argentina.
Depreciation, depletion and amortization. During the three-month periods ended September 30, 2021, and September 30, 2020, we incurred depreciation, depletion and amortization expense of approximately $0.1 million and $0.2 million, respectively.
Interest and other expense, net. We recorded a nominal amount of interest and other expense, net for both the three-month periods ended September 30, 2021 and September 30, 2020.
Gain (Loss) on foreign currency losses. We recorded a foreign currency gain of approximately $0.1 million for the three months ended September 30, 2021. We recorded a nominal foreign currency loss for the three months ended September 30, 2020. 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 US dollars.