Regarding Mesa mining:
Since the light gray, white, yellow and dark green/brown clays have been getting scarce at the clay mine, I went ahead and began a new mine. The mine entrance is located immediately east of the portal (within the portal's glass wall). If you follow the single-wide tunnel you will find three underground veins containing (from top to bottom) white, light gray, dark green/brown, and yellow.
This mine is entirely underground. I have had my fill of the stuff, so it is completely open to whoever. The mine is entirely beneath a very broad Mesa plateau. I would prefer the outside walls of the mine not be breached so the mesa's pretty bits remain so.
The veins beneath the plateau are very broad, so you should be able to get what you want without disrupting the surface.
Cheers.
