Why is depletion expense not a operating expense

RL Company Income Statement Sales Revenue Less: Cost of Goods Sold Gross Profit Operating and Administrative Expenses: 1,000,000 -$300,000 $700,000 Administrative Expense Adertising Expense Amortization Expense Depreciation Expense Rent Expense Salaries Expense Supplies Expense Utilities Expense Total Operating& Administrative Expenses $25,000 14,000 $10,000 $15,000 $14,000 74,000 $1,000 $48,000 $201,000 499,000 Operating Income Other Revenues and Expenses: Gain on Sale of Equipment Depletion Expense Interest Expense Total Other Revenues and Expenses $10,000 42,000 $8,000 Earnings Before Income Taxes Less: Income Tax Expense Net Income 40,000 459,000 $50,000 409,000