North To Phosphoria

- Calcite Crystals on Phosphoria Fm Limestone

A little while back, my recent visit to Dishpan Butte really highlighted my disappointment with the rock hunting scene south of here. Over the decades, it’s dwindled from its once unlimited potential to a current letdown. I have to admit, part of this disappointment stems from the absolutely fantastic location I used to call home.

But hey, all hope isn’t lost! There’s still some rock hunting potential to the north that hasn’t been hammered by as much collecting pressure. Plus, there’s a recent quarry in a Phosphoria Formation outcrop. Could that vivid orange-red to yellow fluorescent calcite, like the one I stumbled upon near Swift Creek, be waiting there? Since it’s the same formation, it’s time for another adventure heading north!

This one is totally spur-of-the-moment, but it’s close and reasonably accessible. So, minimal prep needed! Just hop in the car, and I’ll be there in under an hour. And guess what? My 92-year-old mother is joining in! I’ve been to the Bridger Mountains many times over the years, but it’s been a while since I explored them with her—back when we used to hunt deer when I was a kid. As she likes to say, “We’re no spring chickens.” LOL!

This time of year, driving beyond the valley means leaving the lush greenery behind. The irrigation water works its magic, turning the landscape into a canvas of tall corn, blue-green grain, and emerald alfalfa, all topped by a sea of fragrant purple blossoms. Quite the contrast!

- Leaving This Watered But Almost Rock-Free Land

- For This Almost Waterless, But Jagged Rock-Filled One

Leaving the green landscape, an old, single-track dirt trail up a seasonal creek bottom has been replaced by a double-lane, all-weather gravel road streaking dustily across the flats. This new road provides quick, easy access and leads to a recent quarry exposing a jumbled Phosphoria Formation. More people, yes, but also more freshly exposed rock!

The Geology

It’s a complex place with faulting, folding, thrusting, and overturning that exposes and alters an entire geologic column. This mashup increases the chance of finding some interesting combinations that might be uniquely fluorescent. I’m targeting the Phosphoria Formation because of its karst features that foster open spaces and contain crystals.

Check out this illustrated road log that describes the geology in the Wind River Canyon, just a few miles west of this adventure.

- Phosphoria Limestone Outcrop

The Quarry

- In the Quarry

- Looks Like She’s Found a Few Keepers!

There are some interesting rocks here, and it’s easy collecting for my mother. But for me? Not so much. I was hoping for some vuggy limestone with multiple generational calcite crystals, but no such luck. A few rare, very small, clear, single-generation calcite crystals escaped quarry activity. Just some calcite veining and a single fossil shell.

Not quite what I was hoping for! No indication of fluorescence in rocks shaded from the sun. Still, I gathered a few interesting samples to test at night.

Beyond the rocks, what a beautiful day to be out and about with my mother! That’s a treasure in itself—the joy of sharing.

- An Adventure to Remember

And yes, that’s my 92-year-old mom recording memories on her smartphone.

Finds

Beyond the joy, here’s what I hauled home:

- Quarry Rocks

- Fluorescent Quarry Rocks Under Long Wave Ultraviolet

Oh my gosh! Those initially unpromising daylight rocks had some very surprising glows: aqua, yellow, dull orange, bright long-glowing phosphorescent white, and the most surprising of all—lavender veins with occasional bright yellow or bright lavender star-like spots.

Fluorescent rock hunting in daylight is a hit-and-mostly-miss activity at best. I never suspected much from their daylight appearance, but these finds demand a return night visit. The most intriguing find was that small, transparent single-generation calcite crystal. It glowed a delicate lavender while illuminating and maintained its transparency. Pure, beautiful magic!

- A Calcite Crystal Glowing with Promise

Next adventure? The quarry at night! ✨

Update

Turns out this quarry is actually in a chunk of the Madison Formation, not the Phosphoria like I thought. It’s not the more blocky crystalline facies I’m familiar with, but a more brecciated, calcareous mudstone/siltstone with thin interbedded limestone layers. And the faulting has placed it adjacent to some very Amsden-looking stuff.

Cheers,
D 🪨🔥