According to the geology books, there are no Silurian rocks in Minnesota. Elsewhere there is evidence of primitive plant life, mosses and corals. There may have been vascular plants. But Minnesota was a barren peneplain covered by a very hot sea. The equator passed right through the middle of the state.
I am about to fill in gaps in my rock inventory with a few ordered items: turquoise in forms ranging from good quality cabochons to chalk to beads; carefully chosen fossils including coprolite, and my continuing acquisition of affordable examples of the traditional and alternative birthstones. I opened the tumblers and found that most of the materials have to go back in. Haven't gotten together with the "ladies" to do wirewrap yet. I gathered up all the white rocks for prep and painting during the coming winter...which unfortunately is on its way.