Overview

Copper Ore from Mystical World spawn in the world, alongside the correct copper ore of Thermal Foundation. This does not appear to be intentional, as it's a hassle to deal with and appears to be the only existing duplicate ore type. Silver Ore from Mystical World does not appear to spawn. does also spawn. This is likely an issue with Mystical World's config.
This isn't a big problem, as the wrong copper core can be converted into the correct one easily with the crafting bench, but the spawning behaviour is likely unintentional nonetheless.

It is worth noting that no Mystical World ores, be they the duplicates or its unique Amethyst ore, spawn in the Mining dimension.