26 CFR § Percentage depletion rates. | CFR | US
(3) Other minerals. A rate of 15 percent is applicable to the minerals listed in this subparagraph regardless of the situs of the deposits from which the minerals are produced, provided the minerals are not used or sold for use by the mine owner or operator as rip rap, ballast, road material, rubble, concrete aggregates, or for similar, however, such minerals are sold or used for