PrairieDog

Bob, I did not knowabout caliche.  But it sounds vaguely similar to the predominant rock in my part of the world, sedimentary limestone.  It does make good building facing material, but its structural properties are nowhere close to that of, say, granite.  So I am now a little wiser.

On the other hand, my previous life consisted of working in a muskeg swamp basin roughly 100-150 miles in diameter.  The US Army used to do manoeuvres there.  I do believe the Sherman tank ultimately got recovered….

Mike