Smythe said:
Geologically, Coticules are extracted from the "Les Plattes" member of the Stavelot massive. Within "Les Plattes" there are 4 Coticule deposits. Tier d'Ol Preu, where the quarry is located has access to one of these deposits. The mine in Regné gives access to another deposit. All deposits contain, next to Coticule layers, also yellow layers of rock that has no, or almost no abrasive properties. Geologists call that pseudo-Coticule. At Ol Preu the situation is fairly simple. There's only one layer, called "La Veine aux Clous, that has only limited abrasive properties. But at other former mining spots, the situation was much more complicated, and
I suspect that a less experiences miner could occasionally mix stones from a pseudo-Coticule layer with thos of a good layer. At Ardennes, the entire production passes through the hands of Maurice Celis, proprietor of the company. But I wonder if this was the same in the old days, when 100000's of Coticules were exported all over the world each year.
I can imagine that some companies, at the verge of stopping activity, didn't worry too much about what they were shipping.
I would be happy to try these stones, Cedrick.
Kind regards,
Bart.
PS. I marked a few words in bold, to emphasize where I was speculating.