Wyoming State Geological Survey

10/14/2026

Mineral Resources: The Geology of Percentages
When Percent Is Too Big

What do geologists do when a percentage becomes buried beneath too many decimal places?

They use parts per million, or ppm, to describe small concentrations without long strings of zeros:

- 1% equals 10,000 ppm
- 0.1% equals 1,000 ppm
- 0.01% equals 100 ppm
- 1 ppm equals 1 gram in a metric ton

If rock contains 1 ppm of an element, a metric ton of that rock contains 1 gram of the element, assuming the concentration is consistent throughout.

Consider Wyoming’s northern Bighorn Mountains.

The Wyoming State Geological Survey sampled the Flathead Sandstone near Bald Mountain. Some rocks here are paleoplacers: ancient deposits where moving water concentrated dense minerals, including those containing rare earth elements.

One sample contained approximately 6,816 ppm total rare earth elements.

That equals 0.6816%, or about 6.8 kilograms (15 pounds) per metric ton, if that concentration remained consistent.

But that “if” matters.

The result describes a single sample, not the entire Bald Mountain area. It is not an average deposit grade, nor does it establish that the concentration extends across a large volume of rock.

One sample can reveal an interesting geologic signal. Determining whether it represents a larger concentration requires systematic sampling, mapping and analysis.

Parts per million may describe tiny quantities, but those quantities can offer important clues about a rock’s geology.

Want to dig deeper? Explore Wyoming’s rare earth geology in the WSGS report Rare Earth Elements in Wyoming:https://www.wsgs.wyo.gov/products/wsgs-2013-ri-65.pdf

Next in The Geology of Percentages: Why tiny impurities can determine how exceptionally pure minerals are used.

Image description: Graphic titled “When Percent Is Too Big.” Photo A shows Flathead Sandstone conglomerate near Bald Mountain, with a rock hammer for scale. Photo B shows sample 20110824WS-D beside a penny. The graphic identifies 6,816 ppm total rare earth elements in the sample and explains that more sampling would be needed to understand the larger area.

10/13/2026

Mineral Resources: The Geology of Percentages**
When 0.1% Is a Lot

One-tenth of 1% sounds like almost nothing. In uranium geology, however, it can represent a meaningful concentration.

Uranium grades are commonly reported as U₃O₈, a standard way of expressing how much uranium is present. A grade of 0.1% U₃O₈ means that roughly one part out of every 1,000 is uranium oxide.

Put another way, one metric ton of rock at that grade contains the equivalent of about 1 kilogram, or 2.2 pounds, of U₃O₈.

That is the amount indicated by the grade. It is not necessarily the amount that could be recovered.

How does uranium become concentrated in the first place?

The southern Powder River Basin in Converse County provides a good Wyoming example.

Groundwater moving through porous sandstone can pick up small amounts of uranium from the surrounding rocks. As long as the water contains enough oxygen, the uranium remains dissolved and travels with it.

Eventually, the water may reach an underground area where oxygen is scarce and the chemistry changes. There, the uranium can no longer remain dissolved. It drops out of the water and accumulates on sand grains and in the tiny spaces between them.

The boundary where this change occurs is called a redox front. Over time, uranium can become concentrated along that boundary, creating a curved mineralized zone known as a roll-front deposit.

The percentage is still only part of the story. Geologists must also consider the deposit’s thickness, continuity, depth, surrounding rock, groundwater conditions, and how much uranium could realistically be recovered. Market conditions, permitting, and environmental review also influence whether development is feasible.

In mineral geology, a small percentage can represent a major natural concentration.

Learn more about uranium deposits and roll-front geology in Wyoming:
https://main.wsgs.wyo.gov/energy/uranium/uranium-deposits

Image description: Graphic showing that 0.1% U₃O₈ equals 1 part in 1,000, or 1 kilogram (2.2 pounds) per metric ton of rock. A photograph from Dead Tree Creek, South Australia, shows a curved roll-front boundary exposed in rock and outlined in blue.

10/12/2026

Mineral Resources: The Geology of Percentages
What does 1% look like?

In one metric ton of rock, it equals about 10 kilograms, or 22 pounds, of material.
Suddenly, 1% doesn’t sound quite so small.

But is 1% a lot? That depends entirely on what we’re looking for.

For one mineral commodity, 1% could represent an unusually high concentration. For another, it might not be nearly enough. Geologists also need to know how much rock is present, which minerals contain the material of interest and how much can actually be recovered.

That is where percentages become fascinating.

These questions matter across mineral resources. Uranium mineralization give us some especially interesting Wyoming examples of how small concentrations can matter. High-purity quartz turns the question around: Its usefulness for advanced manufacturing depends not only on how much quartz is present, but also on how little of everything else remains.

Wyoming gives us some remarkable places to explore these ideas. Uranium deposits occur in porous sedimentary rocks in several of the state’s basins. Rare earth elements are also being investigated in coal, heavy-mineral sandstones, and granitic pegmatites across Wyoming.

Over the next four posts, we’re going to follow the numbers and find out:
How a small percentage can add up to a surprising amount
Why geologists sometimes count elements one part at a time
Why the tiniest impurities can determine how a mineral is used
Why two rocks with the same percentage can tell very different stories, including how much material can actually be recovered

A percentage can tell us a great deal about a rock, but never the entire story.

Sometimes a little is a lot.
Sometimes almost everything still isn’t enough.
And sometimes what makes a mineral remarkable is what isn’t there.

Image description: A graphic illustrates 1% by highlighting one square in a field of 100. It notes that 1% of one metric ton equals 10 kilograms, or approximately 22 pounds.

10/08/2026

This year’s International ShakeOut Day is October 15—one week from today! Join the WSGS and others from around the state in taking time to practice earthquake safety and preparedness as part of the Great Wyoming ShakeOut. Wyoming is earthquake country, and damaging earthquakes can occur in any part of the state. We encourage everyone to participate and sign up at shakeout.org/wyoming. For more on earthquakes in Wyoming, visit main.wsgs.wyo.gov/hazards/earthquakes.

10/06/2026

Yellowstone Has a New Listening Post

How do you keep track of a geyser when no one is watching? Listen.

A new monitoring station near Old Faithful came online in September, giving scientists another way to track Yellowstone’s hot-water systems. Installed by a team from the University of Utah, Yellowstone National Park and the U.S. Geological Survey, the station records ground vibrations, weather conditions and low-frequency sound.

It has already detected geyser eruptions and the distinctive “thumping” of Doublet Pool. By comparing sound signals recorded at different stations, researchers can also locate their source.

These measurements help scientists understand how geyser basins change and improve monitoring of hydrothermal hazards.

Read more: https://www.usgs.gov/observatories/yvo/news/yellowstones-newest-hydrothermal-monitoring-station-and-renewed-camera

Credit: USGS/Yellowstone Volcano Observatory. The image is explicitly marked public domain; no individual photographer is named. U.S. Geological Survey

Image Description: Monitoring equipment stands on sandy ground near Geyser Hill in Yellowstone. Labels identify two covered infrasound sensors, a buried seismometer, an equipment box and a tower holding solar panels, weather sensors and a radio antenna.

09/30/2026

09/24/2026

T. rex Update: Wyoming Fossils and Ancient Body Heat

T. rex has been making headlines this month, with a remarkable Wyoming fossil drawing renewed attention and new research taking the dinosaur’s temperature. Here’s what scientists are investigating—and what they’ve learned.

First, the news from our own backyard.

“Rex Junior,” a partial T. rex skeleton recovered decades ago from the Zerbst Ranch near Newcastle, preserves bones in exceptional three-dimensional alignment. Paleontologist Paul Sereno and his team continue the painstaking work of exposing and studying the specimen.

Could it reveal more about what T. rex looked like? That’s the exciting question. Some much-discussed findings are still awaiting publication, so the next chapter remains a work in progress.

Meanwhile, another team has investigated a different question: How warm was T. rex?

How do you take a dinosaur’s temperature about 66 million years after it lived? Start with its teeth.

Researchers analyzed chemical signatures preserved in T. rex tooth enamel and estimated a body temperature of about 97°F—remarkably close to our own. Teeth from crocodilians that lived alongside it recorded cooler temperatures, adding evidence that T. rex maintained body heat above its surroundings.

Those teeth hold clues to more than temperature. They help scientists investigate how this enormous predator powered its body and which climates it could tolerate.

Even one of the world’s most famous dinosaurs still has secrets—and Wyoming’s rocks are helping scientists investigate them.

Photos: Two views of a Tyrannosaurus rex display at the Palais de la Découverte in Paris, photographed by David Monniaux/Wikimedia Commons. Both images are licensed under Creative Commons Attribution-ShareAlike 3.0: https://creativecommons.org/licenses/by-sa/3.0/

These illustrative photos do not show Rex Junior or the specimens used in the temperature study.

09/22/2026

One Creek. Two Oceans.

At one extraordinary spot in Wyoming, a single creek reaches the Continental Divide,and flows toward two different oceans.

Deep in the Teton Wilderness, North Two Ocean Creek enters a broad mountain meadow known as Parting of the Waters. There, the creek splits.

One branch becomes Pacific Creek, beginning a journey through the Snake and Columbia rivers to the Pacific Ocean.

The other becomes Atlantic Creek, flowing through the Yellowstone, Missouri and Mississippi rivers before reaching the Gulf of Mexico and the Atlantic drainage basin.

As if that were not remarkable enough, the Continental Divide here is so low and gentle that during wet spring conditions, fish can cross from one watershed into the other. Scientists believe Yellowstone cutthroat trout likely used this route to reach Yellowstone Lake after glaciers retreated roughly 14,000 years ago.

Two Ocean Pass was designated a National Natural Landmark in 1965.

One creek. Two watersheds. Two oceans. And it all begins in a quiet Wyoming meadow.

Learn more from the U.S. Geological Survey:
https://www.usgs.gov/observatories/yvo/news/two-ocean-pass-a-place-where-fish-can-swim-over-continental-divide

Photo by Annie Carlson, Yellowstone National Park. Courtesy of the U.S. Geological Survey. Public domain.

09/21/2026

What happens when dinosaur footprints appear in rocks scientists thought had formed beneath an ancient sea? They rethink the shoreline.

Near Shell, Wyoming, the Red Gulch Dinosaur Tracksite preserves hundreds of dinosaur footprints made approximately 167 million years ago. The tracks occur in limestone deposited along the Sundance Sea during the Middle Jurassic.

Before the tracks were reported in 1997, most scientists interpreted the Bighorn Basin, and much of Wyoming, as having been covered by the sea during this interval. The footprints, together with ripple marks preserved in the rock, revealed a broad, shallow tidal environment with enough exposed land nearby to support dinosaurs, other animals and plants.

A footprint is a type of trace fossil: evidence of an organism’s activity rather than part of the organism itself. A single footprint is called a track, while a sequence made by one animal is a trackway.

Most of the identifiable trackways at Red Gulch point south-southwest. Scientists have considered several possible explanations, including group or migratory behavior and environmental conditions that guided the dinosaurs across the tidal flat. The footprints tell us where the animals went—but not yet why they went there.

Learn more about the Red Gulch Dinosaur Tracksite and plan a visit through the Bureau of Land Management:
https://www.blm.gov/visit/red-gulch-dinosaur-tracksite

If this puts you in the mood for more Wyoming paleontology, the Tate Geological Museum at Casper College will host its free Fossil Day from 10 a.m.–2 p.m. Saturday, Oct. 10:
https://caspercollege.edu/tate-geological-museum/

Photo: Bureau of Land Management Wyoming/Bob Wick