Mine gross profit. For the three months ended March 31, 2023, we recorded $12.3 million mine gross profit compared to $6.8 million mine gross profit for the same period in 2022. The increase is primarily attributable to higher sales and lower cash cost after by-product credit per ounce sold, as discussed above.
General and administrative. For the three months ended March 31, 2023, general and administrative expenses of $1.1 million did not materially change from the same period in 2022.
Exploration expenses. For the three months ending March 31, 2023, property exploration expenses totaled $3.7 million as compared to $2.5 million for the same period of 2022. The increase was largely due to increased geotechnical and metallurgical studies at the County Line property and the completion of the monitoring well at the Golden Mile property.
Other (income) expense, net. For the three months ending March 31, 2023, other income totaled $0.3 million as compared to other expense of $0.02 million for the same period of 2022. The change is due to an increase in interest income in 2023.
Income and mining tax expense. For the three months ended March 31, 2023, income and mining tax expense was $1.5 million as compared to $0.4 million for the same period in 2022. The increase is the result of our higher income before income and mining taxes and increased Nevada net proceeds of minerals tax due to higher metal sales. See Note 4 to the Condensed Consolidated Financial Statements.
Net income. For the three months ended March 31, 2023 we recorded net income of $6.4 million as compared to $2.6 million in the corresponding period for 2022. The increase is due to the changes in our consolidated results of operations, as discussed above.
Non-GAAP Measures
Throughout this report, we have provided information prepared or calculated according to U.S. GAAP and have referenced some non-GAAP performance measures which we believe will assist with understanding the performance of our business. These measures are based on precious metal gold equivalent ounces sold and include cash cost before by-product credits per ounce, total cash cost after by-product credits per ounce, and total all-in sustaining cost per ounce (“AISC”). Because the non-GAAP performance measures do not have any standardized meaning prescribed by U.S. GAAP, they may not be comparable to similar measures presented by other companies. Accordingly, these measures should not be considered in isolation, or as a substitute for measures of performance prepared in accordance with U.S. GAAP. These non-GAAP measures are not necessarily indicative of operating profit or cash flow from operations as determined under GAAP.
Revenue generated from the sale of silver is considered a by-product of our gold production for the purpose of our total cash cost after by-product credits for our Isabella Pearl Mine. We periodically review our revenues to ensure that our reporting of primary products and by-products is appropriate. Because we consider silver to be a by-product of our gold production, the value of silver continues to be applied as a reduction to total cash costs in our calculation of total cash cost after by-product credits per precious metal gold equivalent ounce sold. Likewise, we believe the identification of silver as by-product credits is appropriate because of its lower individual economic value compared to gold and since gold is the primary product we produce.
Total cash cost, after by-product credits, is a measure developed by the Gold Institute to provide a uniform standard for comparison purposes. AISC is calculated based on the current guidance from the World Gold Council.
Total cash cost before by-product credits includes all direct and indirect production costs related to our production of metals (including mining, crushing and conveying and other plant facility costs, royalties, and site general and administrative costs) plus treatment and refining costs.
Total cash cost after by-product credits includes total cash cost before by-product credits less by-product credits, or revenues earned from silver.