I have a lot of unopened Mazon Creek concretions and though I do put some out in the winter for the Freeze / Thaw process, the vast majority, especially the larger ones do not open. So to dwindle my concretions, I have no problem whacking them with a hammer, and that is what I was doing today. As we all know, this is not the best way to do it since it can damage a nice specimen, but I take my chances.    I always picked up any concretion that looked promising and never passed up larger