Hi Chris, the bone / coprolites / phosphatic nodules will be obvious, but there might be teeth in there and who knows what else! I was given a lump of bone bed from Lavernock a while ago and it had a dark 'crust' of a few millimeters on one face. When I looked at it under my stereo microscope at x10 (a loupe is good as well) I found a few unusual (up to 5mm) bits of black and it turns out that they are Cephalopod hooklets! These, along with some other fossils were only recognised in the Rhaetion - Penarth bone bed and documented in a paper published in 2017 at Bristol University - La n d o n , E . N . U., Duffin, C. J., Hildebrandt, C., Davies, T. G., Simms, M. J.,
& Benton, M. J. (2017). The first discovery of crinoids and cephalopod
hooklets in the British Triassic. Proceedings of the Geologists' Association,
128(3), 360–373. https://doi.org/10.1016/j.pgeola.2017.03.005
The ones I have found look different to those illustrated so my research goes on!
So, the moral of this story is to look at what you have carefully and to dissolve the matrix in Acetic acid (white vinegar) and then re-examine it. Teeth are a litle more obvious!
Also, bone bed is tough to prep with an air pen, but grinding and polishing can be good. See previos post by P King Chef!