This is a nice, proetid trilobite of the Gerastos genus from an unusual location, Jorf, Morocco. The rock here is very chert-like with a glassy appearance. The locality has a huge diversity of trilobites but I've only seen a handful of Gerastos from the location. This specimen is .8" in length and very inflated. It has a deep reddish color, because the shell is actually pretty translucent so it's taking on the color of the rock underneath.
Trilobites were a very diverse group of extinct marine arthropods. They first appeared in the fossil record in the Early Cambrian (521 million years ago) and went extinct during the Permian mass extinction (250 million years ago). They were one of the most successful of the early animals on our planet with over 25k described species, filling nearly every evolutionary niche. Due in large part to a hard exoskeleton (shell), they left a excellent fossil record.