When I was looking in 1993 for a good rough agate specimen that should cut into a fine birthday-present for my wife, some uruguayan specimen from Artigas passed by. I bought some of these weak coloured but nicely banded nodules to work with.
Some of this specimen changed their pattern while drying over the years. Especially the mortar that I cut - the reason is the intensively care that it got in the dish-washer.
These specimen do not show so much of the “water-level-pattern” - only in the center. The pattern is nicely deformed and is showing a lot of exhausting-ventiles.