1.
platinum
A precious silvery-white metal used in jewelry, catalytic converters, and various industrial applications. The Japanese name literally means 'white gold'.
白金の指輪。
A platinum ring.
白金は金よりも希少な金属だ。
Platinum is a rarer metal than gold.
結婚指輪は白金と金のどちらにするか迷っている。
I'm torn between choosing platinum or gold for the wedding rings.
In jewelry contexts, プラチナ (the loanword from English/Spanish) is more commonly used in advertising and everyday conversation, while 白金 is the traditional Japanese term used in science and formal contexts. Note: 白金 (read しろかね) is the place name for the Shirokane district in Tokyo. The element symbol is Pt. Related: プラチナ (platinum — loanword, common in jewelry marketing), 金 (gold), 銀 (silver).