What is this!?

I haven't a clue, but someone might drop in with something during daylight in North America.

Thanks, I hope so.. I was able to put a small chip in it with a hammer, but I cannot scratch it.

Sedimentary rock apparently worked by Skolithos Linearis (Cambrian worm)..

Are you in the UK, by chance?

The Scolithus(sp?) looks like its in a type of chert. Thats a rarity for these critters. It could be lower Ordovician or LAtest pre-Cambrian . That broadens the search fields to inclue maybe 20 countries including UK.

sp may be linearis, dont know and couldnt be sure from the "Treatise of Invert Paleo". Theres about 7 actual speies, the separation of which is made mostly from the tubule structure and Im not savvy enough to pick out whether the Scolithus tubules are laterally lined, composited, or displaying a "feathery lineatio

This was found about 70 km west of the mississippi in Ia, US. What I found peculiar was, it was the ONLY rock around, laying on surface of an open dirt field, that was being used as a tree nursery. I can take more pictures if anyone wants better view. This has baffled me for the longest time, and I aappreciate the experitise.

It looks as if it were moved about and the edges smoothed a bit. So, Its an ancient rock. (Iowa has scolitus tubes in rocks lenses but as I recall, the biggest deposit re in the North nd are of Silurian age. Scolithes are, as a group, not a fossil that we use for any age determination since it s found throughout the Paleozoic rocks.
It may be (Im just guessing here) that the chert is a glacial erratic (it was dragged or "rafted" on glacial ice cubes or left in a morine. The Nbraskan/ Illinoian advnces did make it to Iowa (Actually three of the four big ice advances covered Iowa so glacil erratics and rafted rocks are quite common along with wind deposited soils that ajoined glacier paths

the rock containing the fossils has a separate story of its genesis, and Its winding up in your field is another story entirely. That s what I should have simply stated