Hafnium (element)
鉿 is a rare kanji that refers specifically to the chemical element hafnium. It has no broader conceptual meaning beyond this technical use.
鉿 is a modern character created to represent the element hafnium. It combines the metal radical 金 with the phonetic component 合 (ゴウ・ガッ), which suggests the reading コウ.
The metal radical 金 hints at a metallic element, and the right side 合 (join) suggests hafnium's use in alloys or its discovery alongside zirconium. Together they point to the element hafnium.
For コウ, imagine a chemist saying 'Co' (cobalt) but correcting to hafnium: 'Co' -> コウ, and the metal radical 金 reminds you it's an element.