I found this piece of clam in some pretty hard matrix along the beach below the tourist information building last year around this time while visiting Haida Gwaii. I've only just worked away most of the matrix. The inside was softer sand/clay which ground out quickly with my Dremel but had to use the diamond cutter to work off a lot of the matrix covering the outside. You can see in the photos that only a few of the 'fingers' survived fossilization. As this was on the beach I am not sure how old it could be, maybe Jurassic or as old as Triassic? Need help.