precious metal

Japanese: precious metal（英語表記）preciousmetal

...Chemically, it occurs as an element, has a low tendency to ionize, does not react directly with acids, and is not easily oxidized in air, so in addition to the metals mentioned above, copper (Cu) and mercury (Hg) are also included in the term. [Nakahara Katsumasa]
[Precious metals as metallic materials]
In the classification of metallic materials, gold, silver, platinum group metals and their alloys are collectively called precious metals. In terms of classification based on the tendency to ionize, which is one of the chemical properties, in addition to the above metals, mercury and copper are also included in the noble metals.

[Metal]

…Most of the others are base metals. For decorative purposes, gold, silver, platinum and their alloys are called precious metals. Gold, silver and copper are also called coinage metals because they are used as currency. …

*Some terminology explanations that mention "precious metal" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…化学的には，単体として産し，イオン化傾向が小さく，酸類などとは直接反応しにくく，空気中では酸化されにくい，ということで，上記の金属以外に銅Cuおよび水銀Hgをも含めていうのが普通である。【中原勝儼】
［金属材料としての貴金属］
　金属材料の分類では，金，銀，白金族金属およびそれらの合金をまとめて貴金属precious metalという。化学的性質の一つであるイオン化傾向から分類すると，上記の金属のほかに水銀，銅なども貴金属noble metalに含まれる。…