What Is That Weird Boulder Dug Up On Historic Wyoming Ranch?

In a trench meant for a sewer line, a Wyoming ranch family found a massive, nearly spherical boulder that was so out of place, it left them bursting with questions.

Scott Coale and his son William, 18, were digging a trench recently on the Hogg Ranch near Meeteetse, a historic homestead that had been in Scott’s family for over 100 years.

A stubborn and unexpected obstacle blocked the ditch they were digging, interrupting their work.

They found they'd struck a huge boulder that by all appearances, shouldn’t have been there.

“We'd been in putting in a sewer line to a cabin,” Scott said. “There's no rocks here at all. We were having smooth sailing, and then, all of a sudden, the backhoe struggles.”

William got out of the skid steer he was using to backfill and was surprised by what he found.

The Discovery

“I asked him how big it was because it was in the middle of our ditch to run the sewer line,” Scott said. “He tells me that it is as big as the side-by-side. At first, we're just kind of joking, but then I realize I don't know if I can get it out.”

Scott called a friend with a backhoe and they tackled the boulder.

“I had some daylight left and got on the side of it and started digging,” he said. “Next thing I know, I got it out the hole with the backhoe. It was this big old round rock. It just amazed us that it was so perfectly round.”

They set the rock to the side and resumed their chores, although distracted as they tried to figure out what they had found. The boulder is about 4 feet tall and 4 feet wide.

“It's just weird,” Scott said. “The geology of Wyoming is a great thing. You never know what you're going to find.”

The family was especially surprised to find the giant boulder because the area it was unearthed in is devoid of rocks.

“I've never personally seen anything like that,” William said. “We were just digging and then bam, there is this big old boulder in the ground that's not normally shaped.”

What On Earth Had They Found?

Unsure of what they had unearthed, Scott’s wife Diane posted the find on the Facebook page Wyoming Rockhounder. She asked if they should try to open it and see what was inside.

There was much debate, but the consensus from other rock enthusiasts was that it’s a sandstone concretion.

“I thought it was interesting that people commented about maybe it was a geode or what might be in it,” Diane said. “So, we did a little bit of research and the geodes are found in limestone rather than sandstone.

“The likelihood of us cutting it up and finding a geode is probably pretty minimal, so we kind of want to leave it the way it is.”

That is a good idea, said geologist and owner of Ava’s Silver and Rock Shop in Thermopolis.

Ava Cole has more than 50 years of experience in the field and is familiar with this type of rock.

“There's quite a few places around Wyoming that have them,” Cole said. “Sometimes there are iron stains in the middle of them, but they're not worth cutting into — unless you want to sharpen your blade.”

Just A Rock

Concretions are commonly misunderstood geologic structures, according to the Paleontological Research Institution.

Often mistaken for fossil eggs, turtle shells or bones, they are not fossils. They’re rocks. This common geologic phenomenon occurs in almost all types of sedimentary rock, including sandstones, shales, siltstones and limestones.

There may be fossils surrounding the concretions if it’s in shale but not inside the rock itself.

“The concretions that you find in the shale may have fossils in the shale or crystals,” Cole said. “The concretions themselves are just sandstone. There are no fossils in them. The fossils are not in the sandstone layers, they're in the shale layers.”

These concretions form inside sediments before they harden into rocks in continuous layers around a nucleus such as a shell or pebble.

Rates of this formation vary, but can sometimes be relatively rapid over as short a period as months to years, the Paleontological Research Institution reports.

“There's a void in the ground,” Cole said. “It's like a magnetism to them that attracts different minerals until the sand forms tightly around them. There's some kind of quartz in it, too. It's microscopic, but they're not hollow or anything like that. Not like a geode.”

What Do You Do With It?

“I've collected them before and sold them, but don't get much money out of them,” Cole said. “Even if the family wanted to, they probably couldn't get anybody to cut it because it is a pretty good-sized rock and you'd have to have a big diamond saw to cut it.

“Anything that big [when] you cut it open, it would be futile because what's on the outside is mostly on the inside.”

Her suggestion is to let it just sit around in the yard - since it’s always nice to have a round circle rock hanging around.

That is exactly what the Coales plan to do.

“It's going to be a yard ornament,” Scott said. “I want to be able to showcase it in our front yard. I think it's cool.” 

Collecting Your Own Yard Ornament

These concretions are found throughout the Cowboy State and can be collected even on BLM land.

“A lot of people pick them up,” Cole said. “Between Worland and Ten Sleep, on Rattlesnake Ridge, there's a whole bunch of them, all different sizes and shapes since they're not always round. They can be like a peanut or anything like that.”

The Coale family are already avid rockhounds. They have interesting formations on their property that they explore and one area on the historic ranch is dubbed Death Valley because, according to William, it looks like the badlands.

That was why they were even more surprised to find this rock in an area where they normally would not be looking. 

“I'm the rock person in the family,” Diane said. “We'd always go find petrified wood and stuff ever since I was a kid but I'm pretty excited about this rock.”

This plain, nearly perfectly round boulder has been added to their family collection as the centerpiece.

Jackie Dorothy can be reached at jackie@cowboystatedaily.com.