Income Taxes	6 Months Ended
Jun. 30, 2019
Income Taxes
Income Taxes	10. Income Taxes The Company has estimated that its effective income tax rate for 2019 will be 20.1%. The primary reason for the effective income tax rate being below the federal statutory rate is due to statutory depletion, which is allowed for income tax purposes and is a permanent difference between net income for financial reporting purposes and taxable income. In 2018, the effective income tax rate was further reduced from the federal statutory rate due to research and development tax credits associated with the construction of the St. Clair kiln project.

Income Taxes

6 Months Ended

Jun. 30, 2019

10. Income Taxes

The Company has estimated that its effective income tax rate for 2019 will be 20.1%. The primary reason for the effective income tax rate being below the federal statutory rate is due to statutory depletion, which is allowed for income tax purposes and is a permanent difference between net income for financial reporting purposes and taxable income. In 2018, the effective income tax rate was further reduced from the federal statutory rate due to research and development tax credits associated with the construction of the St. Clair kiln project.