Fossil Butte National Monument

A Museum You Should Visit

Fossil Butte National Monument is about 20 miles from Kemmerer, Wyoming, and well worth a visit.

The visitor’s center has a nice view of its namesake butte, which has a 50 foot deep layer of pale, fossil-bearing Green River formation limestone from 52 million years ago.

It also contains some really great fossils from the same limestone. They’ve got a few massive turtles, an articulated crocodile, some freshwater stingrays, and tons of fish fossils. I only had the sense to take a picture of one exhibit, great examples of the kind of fish fossil I found.

American Fossil commercial fossil quarry

While I was in Kemmerer, WY, I did a 4-hour session of fossil hunting at the American Fossil quarry.

American Fossil bills itself as The World Leader in Paleo-Tourism.

They give you a geology hammer, and a “chisel”, a flat piece of sheet steel vaguely sharper at one end than the other. They set out like an acre of limestone rocks. You choose one. set the chisel in a likely depression or groove and tap it with the side of the hammer. With a little luck, you split the rock along a natural weak layer, and reveal a fossil. I split a whole lot of limestone in my 4 hours. I did get a few fish fossils, including these decent little “herring like” knightia.

The rock is surprisingly easy to split. After reading a little bit about the Green River formation, I think the dry season layers are structurally a little weaker. The rock seemed damp to the touch after splitting. I don’t know if this is ground water that percolates through the limestone, or if it’s 50 million year old fossil water. After only one day of drying, my pieces of rock gave the impression of being compressed dust. American Fossil recommends making a solution of 1 part Elmer’s glue to 20 parts water, and brushing that solution over the fossils. I did this, it kept the limestone (or “lime mud”) from being too dusty to display.

I can recommend the American Fossil quarry. There’s ample limestone, and they provide the tools. There’s porta-potties on site. It is out of cell phone range as of 2024, and it’s a longish drive off a paved road. I do have to give it an F for accessibility. There’s almost no way someone in a wheelchair could do this.

If you go, take clothing and hats to ward off the sun. Early in the morning, the quarry was cool, but it warmed up fast, and the sun and wind were merciless. Sunglasses, wide-brimmed hat, long sleeves and sunscreen are necessities. Bring a lot of drinking water, too. American Fossil has drinks for sale, but you’ll want plain old water. The parking lot is very close to where you split rocks, so you can leave a cooler in your car.