Rhodium (element), Ruthenium
銠 is a character used for the chemical element rhodium. The alternate meaning ruthenium appears to be a historical misassignment or confusion, but the primary modern sense is rhodium.
銠 is a modern coined character for the element rhodium, combining the metal radical 金 with the phonetic component 老 (ろう). It was created in Japan during the Meiji period as part of the systematic naming of chemical elements.
The left side 金 means metal, and the right side 老 suggests the sound. Picture an old (老) metal (金) coin made of rhodium, a rare and valuable element.
For ロウ, imagine a row of old metal rhodium bars: row -> ロウ, and the old metal bars are lined up.