Colorado Revised Statutes Title 34. Mineral Resources § 34-54-102. Sale of ores and minerals

It is unlawful for any person, whether acting for himself or as agent for another, to sell or to purchase any ores, concentrates, or amalgams bearing gold, silver, tungsten, vanadium, uranium, molybdenum, or other rare minerals, or to sell or purchase gold dust, gold or silver bullion, nuggets, or specimens of a value of ten dollars or more, unless at the time of the sale the vendor shall sign with his true name and deliver to the purchaser a memorandum in which he shall state the date of the sale, his residence, the nature and amount of the article sold, the source from which the vendor obtained the same, and the consideration actually paid.