We've heard all about arastras used to break ore-bearing rocks, but what
about the clay and soil grinding machines that look just like arastras?  I
don;t recall what they were called, bu I've seen them in various sizes from
portable to horse powered with 5 foot stones used in preparing materials
for brick, adobe, and pottery.  Brick bats and pottery wasters could also
be ground in them and mixed with the clay.

        Dan W.