Diamond is often used in industry to make cutting tools.
Tips
usage
金刚石 is the technical/mineralogical term (especially in industry, science). For jewelry/ornamental diamonds, 钻石 (zuànshí) is more common.
memory
金刚 (jīngāng) means 'diamond-hard / vajra' in Buddhist contexts, plus 石 (stone). Same 金刚 appears in 金刚经 (Diamond Sutra) — the metaphor of indestructible hardness.
