as far as I have been able to find info,there was one pit here locally that was the only place they were finding this type of calcite still in there og clam matrix's.they closed it now and filled it in with water,if I remember right its
4-5cm specimins would go for under 50 bucks,so no unfortunately,its not huge money,but it wasnt about the money,i like the fact that it is close to a million years old...link....The age of these Mercenaria fossils is late Pliocene to early Pleistocene (1 – 1.5 million years old).