A recent addition to my collection is this piece of black shale from the Whetstone Gulf formation, Ordovician (Sandbian stage) near Worth, NY. It's been prepped to expose some exquisitely preserved Triarthus eatoni trilobites cavorting on an algal frond. The fossils are preserved by pyrite and minute details of the trilobites are present such as their antennae and legs. Some specimens also have the gills and mouth parts preserved. This rock comes from a layer similar to the one exposed in Beecher's Trilobite Bed which is a famous area in Cleveland Glen near Oneida, NY. It was excavated and prepared by the group known as Gold Bugs. Check out their website for some great pictures of other fossils they have found as well as info on the deposition and excavation of the fossils.