26 CFR § Percentage depletion rates. | CFR | US ...
(iv) 10 percent Asbestos, 1 brucite, coal, lignite, perlite, sodium chloride, wollastonite. (v) 5 percent Brick and tile clay, gravel, mollusk shells (including clam shells and oyster shells), peat, pumice, sand, scoria, shale, stone (except dimension or ornamental stone). If from brine wells Bromine, calcium chloride, magnesium chloride. (2) Production from United States deposits.