prov:value
| - See D. Barringer & J. Adams, The Law of Mines and Mining, p. cxxv (1900) (list of 46 nonmetallic minerals that possess commercial value, but not listing gravel); D. Barringer, Minerals of Commercial Value (1897) (listing over 350 substances, including clay, petroleum, phosphate, salt, but not listing sand or gravel); 2 C. Lindley, supra, ?? 424, at 996-997 (recognizing Department's policy for com
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