Skip to body

Central Washington University

Murdock Research Laboratory at CWU Analyzes Authenticity of Ellensburg Blues

Tuesday, May 25, 2021

Anyone who has ever wondered if they were in possession of a precious Ellensburg Blue Agate now has a way of finding out for sure.

Dr. Angela Halfpenny, the Murdock Research Laboratory manager at Central Washington University, has been using the lab’s analytical instruments to test hundreds of mineral samples and develop a way to validate the authenticity of “Ellensburg Blues,” a distinct variety of blue agate that traces its origins to the Kittitas Valley. 

Halfpenny and Sydney Dale, an undergraduate student performing research credits in the laboratory, have been using a portable X-ray spectrometer (pXRF) to measure the chemical makeup of the mineral samples and determine if they are, in fact, Ellensburg Blues. 

After collecting data from hundreds of specimens since her arrival at CWU in 2017, Halfpenny has been working with Dale since last fall to develop a chemical profile of what sets Ellensburg Blues apart from similar minerals, such as Holly Blues, Montana Blues, Mexican Blues, and African Blues.

“What we’ve been finding with Ellensburg Blues is that there’s a huge spike in zirconium — much more than any other blue quartz,” said Dale, who presented her research virtually at last week’s SOURCE conference. “The hypothesis is that Ellensburg Blues have a distinct trace element fingerprint that is different from other blue quartz minerals.”

Halfpenny added that there is a correlation between the depth of the blue color and the amount of zirconium found in the sample.

“Ellensburg Blues are special because they have a very limited area where they grew,” she said. “The entire location where they are found isn’t that big to begin with, so they are quite rare.”

Rock collectors from around the Northwest often visit Kittitas County rock and gem shops to find the elusive yet mesmerizing variety of blue agate. Halfpenny proudly owns a handful of samples, but most of the minerals she and Dale have been testing at CWU have come from community members and an Ellensburg Blue mine claim owner named Carl Carlson.

“Carl’s family has been mining there for 40 years and they have a great archive of samples,” Halfpenny said of the Carlson mine claim off Reecer Creek Road. “They have kept examples from all of the different veins they have found over the years, and as we look at the differences, we typically see a layered profile changing from a dark blue layer at the outer edge changing to lighter blues, and eventually clear colors as you move towards the middle.”

Halfpenny added that the specimens have grown in veins that likely resulted from fluids accumulating at depth millions of years ago. That activity forced the rocks to give and take so they could accommodate the changes.

“That process left the rocks with fractures, which the fluids eventually flowed through,” she said. “The minerals grew out of the fluids as they flowed through the veins, and that resulted in the blue quartz that we call Ellensburg Blue.”

Now that Halfpenny and Dale have collected data on hundreds of Ellensburg Blue samples, they can graph that information and determine what sets these specimens apart in terms of their chemical composition. 

Dale, a former geology major now studying geography, said seeing all of the data on a single chart helped her understand that scientific research can have significant real-world applications.

“At first, it was just running rocks through the equipment and collecting data, but once we started graphing a spectrum of results, it was really interesting,” she said. “We could truly understand what we were looking at, and we realized that zirconium is extremely important to Ellensburg Blues. It’s been nice to finally see the whole picture.”

Halfpenny said understanding the minerals’ chemistry is what allows researchers to determine why certain rock varieties stand apart — and, ultimately, why Ellensburg Blues are more valuable than their look-alikes from around the world.

“This study is about why certain minerals become colored, and how they become colored,” she said, adding that the next phase of the project is to analyze other colored quartz varieties, such as amethyst, smoky quartz, and rose quartz.

“The more measurements you get, the more precise your database becomes,” she continued. “And I would like to take that same approach with the other quartz varieties I’ve been studying over the years.”

Media contact: David Leder, Department of Public Affairs, David.Leder@cwu.edu, 509-963-1518.

Take the Next Step to Becoming a Wildcat.

Admissions@cwu.edu