A person exercising any privilege taxable under Section 757.09 or Section 757.10 and engaging in the business of selling his natural resources or manufactured products at retail in the City shall be required to make returns of the gross proceeds of such retail sales and pay the tax imposed in Section 757.11 for the privilege of engaging in the business of selling such natural resources or manufactured products at retail in this City. But any person exercising any privilege taxable under Section 757.09 or Section 757.10 and engaging in the business of selling his natural resources or manufactured products to manufacturers, wholesalers or jobbers, and in the case of limestone, sand, gravel, or other mineral product, to commercial consumers shall not be required to pay the tax imposed in Section 757.11 for the privilege of selling such natural resource, products or manufactured products at wholesale.