Montana StatutesPart 8. Metal Mines Gross Proceeds15-23-801. Definitions.15-23-802. Metal mines -- ad valorem taxation -- reports and sampling.15-23-803. Valuation -- gross proceeds.15-23-804. Taxation of merchantable value.15-23-805. Imputed value -- procedure for metals.15-23-806. Lien of tax.15-23-807. Assessment procedures.