This strange structure spawned underground. It’s from Astral Sorcery, and the block in the middle started as a stone block. I can keep mining it, and a new ore constantly appears, even ores from other dimensions. Fortune or Silk Touch doesn’t work on it, and it only gives me smelted materials, not ores.

It seems to never disappear, and I essentially get an infinite amount of different resources.

Someone on Reddit told me it’s a glitch.

Never mind. Someone else on Reddit told me that it isn’t a bug. Apparently, it despawns after mining it 200 times.

Edit: Can confirm that the block does not last forever. It is not a bug.