Ah, that makes sense. I would definitely not do 24k gold for anything with a smooth or regular texture. I was curious how durable my gold ring was, so gave it bit of a torture test. I did some weight lifting with it, grabbed some knurled pull-up bars, etc. I took it to sandy beaches, snorkeling, etc. I deliberately banged it against stuff while I was wearing it. Although it got a few good scratches, the weight was exactly the same afterwards: 24.2 grams. A few minutes with a hammer made it good as new. It seems like the metal is soft, but unlikely to separate from itself.

My condolences about the gold coin. I've made similar mistakes. The most frustrating bit for me isn't the damage itself, but the fact that every time you look at the thing, you're reminded of the time you messed up.