This is a cut and polished dinosaur bone slice from Tartarstan in the Takhany District, Volga Region, Russia. The bone is the fossil remains of a Pleseosaur dinosaur. Pleseosaur where large marine dinosaurs that lived approximately 150 million years ago. After death their remains settled to the bottom of shallow seas and where then fossilized or replaced by different minerals including pyrite (pyritized). This is a small piece of a much larger bone that has been cleaned, stabilized, cut and polished to a gem luster. The rear surface and perimeter retains the natural shape in which it was found. It is a small cabinet sized piece that measures 2 7/8 x 2 1/16 x 3/8 inches or 73 x 51 x 9 mm.