C.R.S. § 39-6-104
39-6-104. Classification of mines
39-6-104. Classification of mines. All mines, except mines worked or operated primarily for coal, asphaltum, rock, limestone, dolomite, or other stone products, sand, gravel, clay, or earths, shall, for the purpose of valuation for assessment, be divided into two classes: Producing and nonproducing.