- Forum: General Discussion
Thank you! As I've repeated ad nauseam, sharp jagged grit can scratch polished, flat surfaces which they are technically softer than. Now corundum ("sapphire") is 9 on the Mohs scale, so the quartz in the sand in your pocket at 7, probably won't scratch it, but there could be some garnet in that sand, which at 8, might. Even if corundum is slightly less scratchable, its brittleness and cost make the whole idea ridiculous.