Tbh, I thought vinegar was useless for cleaning rocks until last weekend
I was trying to clean some calcite I found near the river, and my usual water and brush method wasn't touching the iron stains. My kid suggested vinegar, and I figured it was a waste of time. I let a piece soak in a 50/50 mix for about 20 minutes, and the orange stains just fizzed right off. Honestly, I was shocked. I always thought you needed stronger acids for that. Now I'm wondering, what other simple household stuff works for cleaning different minerals without damaging them?
Last year I was convinced my favorite agate was ruined by some weird white crust. Spent twenty bucks on a special cleaner that did nothing. Turns out it was just hard water spots from my own rinse, and a quick soak in some lemon juice cleared it right up. Felt like a total genius after that. For softer stuff like calcite or malachite, I stick to mild things like vinegar or lemon juice now, but I'm too scared to try anything stronger on my good pieces.