You can't build on a Fire Shard in .264. You can't build an altar and you can't build anything else on it. Building an altar for it isn't even an option.
I've only encountered this problem with Fire Shards so far. Earth, Air, Water have been placed just fine.
Note that when placing houses the Fire Shard appeared as an option to place them, but it wouldn't actually allow me to place them there.
