These are the metals gold, silver, and platinum,which are used for coinage, jewelry, and ornaments,and also for industrial applications.Expense or rarity alone is not the determiningfactor; rather, a value is set by law, with thecoinage having an intrinsic metal value as distinctfrom a copper coin, which is merely atoken with little metal value. The term noblemetal is not synonymous, although a metal maybe both precious and noble, as platinum.Although platinum was once used in Russia forcoinage, only gold and silver fulfill the threerequisites for coinage metals. Platinum does nothave the necessary wide distribution of source.The noble metals are gold, platinum, iridium,rhodium, osmium, and ruthenium. Unalloyed,they are highly resistant to acids and corrosion.Radium and certain other metals are moreexpensive than platinum but are not classed asprecious metals. Because of the expense of theplatinum noble metals, they may be alloyedwith gold for use in chemical crucibles.
