TotalyMeow wrote:You posted this in the Bugs section, did you not? But like John said, mines are intended to work the way they do, walls and all. Head to the corners if you want to powerhouse the best ore without making mining clothes.
The section named 'Bugs & Technicalities', not 'Bugs'. And there are many things which are not bugs, but they still belong to this topic.
Anyway, I got an answer from JC and expressed my opinion. How could I know about that invisible wall before I faсed it? It means that now I need to dig the same distance to the corner. Even with ~550 mining I'm getting ~80-85% ore. It ruins all the efforts.
TotalyMeow wrote:No, diagonal purity spreading.
Almost sure it looks like that:

Where the edge of the circle is ~95-100% pure ore, and it 'meets' mine's area close to the corners of the square.