Rough stone

This floor type is automatically created where mountain tiles have been mined away.

Legends claim that this tile can NOT be dirty, needs further testing & proof. (true? bug?)

• https://www.reddit.com/r/RimWorld/comments/acz259/4_reasons_to_never_build_floors_and_a_practical/
• https://steamcommunity.com/app/294100/discussions/0/1752358461538243304/