I think you shouldn't be crippling the liberty of puting blocks in the world because you have flaws in the code design, think about people who decorate with ore blocks or just silk touch ores for later mine them with fortune or someone wants to make a farm with redstone ores using Red Orchids (from ExtraUtils2), maybe a multiblock structure in other mods using ore blocks, etc.
I don't know if you tried this already but in my opinion the best way to fix this issue would be to add a tag to ore blocks that has already been mined and then check if you give or not the bonus (xp or ore, it can be the same tag for both) based on that tag, this way you let people place blocks and not exploit the game with your mod.
I love the mod, and I hope you get to a better solution.
The issue is, the tag won't persist if the block has been placed. Regardless, the feature is configurable, and can be switched to "only duplicated ores can't be placed" or even "every ore can be placed."
I think you shouldn't be crippling the liberty of puting blocks in the world because you have flaws in the code design, think about people who decorate with ore blocks or just silk touch ores for later mine them with fortune or someone wants to make a farm with redstone ores using Red Orchids (from ExtraUtils2), maybe a multiblock structure in other mods using ore blocks, etc.
I don't know if you tried this already but in my opinion the best way to fix this issue would be to add a tag to ore blocks that has already been mined and then check if you give or not the bonus (xp or ore, it can be the same tag for both) based on that tag, this way you let people place blocks and not exploit the game with your mod.
I love the mod, and I hope you get to a better solution.
Regards.