One recent morning near the mouth of a canyon in southwest Colorado Springs, Christine Siddoway placed a few peculiar rocks in a parking lot and a dozen strangers gathered around.

“That’s pretty,” one man said, bringing his eye closer to the peculiarity: a cream-colored stripe across darker granite.

He and the others would soon learn more about the extremely rare, geologic phenomenon that Siddoway has long investigated.

“You all are my first Colorado Springs citizen group I get to show the Tava sandstone to in this way,” the Colorado College professor said at the start of the field trip.

Yes, Siddoway is still getting the word out on this special sandstone she christened years ago — Tava, or Tavakaiv, the Ute name for Pikes Peak.

Like many outdoor lovers around Colorado Springs, the people signed up for this field trip were mostly familiar with Pikes Peak granite, the rock that dominates the region. The general public is far less familiar with the lighter shade of rock embedded within. Tava sandstone is seen as splotchy, red and white rock within granite, forming dikes. It’s seen at Red Rock Canyon Open Space, North Cheyenne Canon Park and elsewhere.

If one knows where to look.

“I think, for the most part, it’s unnoticed,” Siddoway said.

We notice other sandstone, of course: those great formations decorating Garden of the Gods and Red Rock Canyon. Tava sandstone is “utterly different,” Siddoway said.

Less dramatic, one might say. And more significant, a geologist like Siddoway might say.

For more than a century geologists regarded these sandstone dikes as a mystery. Dikes commonly form from intruded magma, not sand. The record is clear about molten rock from the Earth’s core flowing into older fissures and solidifying amid uplift (streaks seen across Black Canyon of the Gunnison are an example).

But sand?

“For a geologist, that really shivers your timbers,” Siddoway said. “You’re thinking, That’s plain wrong.”

Whitman Cross, too, was puzzled by his observations around Ute Pass in 1893. He wrote: “Further detailed study is necessary before a plausible theory as to the origin of these dikes can be advanced.”

A theory is finally emerging. And that’s largely thanks to Siddoway, whose latest research was published last year in the Proceedings of the National Academy of Sciences, alongside colleagues from the University of Colorado-Boulder.

Their theory of Tava sandstone lies within another curious theory. It is a theory known as “Snowball Earth,” a period thought to be some 700 million years ago when the planet, indeed, might have looked like a snowball.

Siddoway and her colleagues summarized their thinking in an article published by The Conversation:

“A giant ice sheet with areas of geothermal heating at its base produced meltwater, which mixed with quartz-rich sediment below. The weight of the ice sheet created immense pressures that forced this sandy fluid into bedrock that had already been weakened over millions of years. … The pressure cracked the rocks and pushed the sandy meltwater in, eventually creating the injectites we see today.”

“That’s our working hypothesis,” Siddoway told guests of her recent field trip.

They were gathered around rock protruding from a hillside just outside the gate for Seven Falls. While others go to the canyon for the towering waterfall, Siddoway has gone for the rock.

Little did she know about this protruding, roadside example just outside the gate when she was riding her bike one day. She almost rode right by.

“I didn’t know the Tava would be right here,” she said. “I almost toppled over.”

She spotted other examples over the years. She’d often be hiking with her chocolate labs when she’d spy some particularly colored block of rock — some chunk that had broken from a larger, higher formation. Siddoway and her canine companions would seek the source above. “If the rocks appeared, then we’d have to prolong our walk,” she said.

The rocks kept appearing, those baffling bands of sandstone. Siddoway “got infected,” she said. “I couldn’t stop thinking about angles and possible ways to figure out.”

She needed to figure out the age — what observers before her struggled to do, since Cross in 1893. Advancements in technology and dating methods centered on zircon, the mineral regarded as a geologic “time capsule,” have allowed breakthroughs since 2014. That’s when Siddoway published a paper in the journal Lithosphere.

“The editor and the reviewers realized that Tava would become a new player in the sparse geological record of the ancient times of Snowball Earth,” Siddoway said.

Further advancements have refined the age of Tava sandstone to around 676 million years. “That puts us squarely in Snowball Earth,” Siddoway said.

Other rocks around the world put us there. But “of all the world localities for sedimentary rocks formed during Snowball Earth, only the Tavakaiv sandstone formed on the mainland of a continent, away from a coast,” Siddoway said.

That ancient continent is known as Rodinia, and that barren place and time are thought to have harbored no life beyond microbial.

Tava sandstone “may show what our continent was like in Rodinia times, leading to changes that gave rise to the explosion of life,” read a colorful pamphlet that Siddoway handed out to guests at the end of her recent field trip.

“Be a Tava lover,” the cover implored. “Discover clues to Colorado’s ancient history — right under your nose (or under your dog).”

The cover depicted Bessie, Siddoway’s late chocolate lab companion. The kids on the field trip loved it.

It was time to go, but they wanted to stay. They apologized.

“No, that’s how you should be!” Siddoway said. “When you’re out exploring is how you discover things!”