Why the risk of wildfires may change some of your outdoor holiday plans.
Untold Arizona: Tracing Arizona’s Turquoise Legacy Through Time
To commemorate Arizona’s birthday, we dispatched our reporters far and wide to bring you stories from the region you've probably never heard before. Hear more from our Untold Arizona series.
Collectors know the names: Blue Bird, Sleeping Beauty, Birdseye. Each evokes a color and pattern, from jade green to deepest robin's egg blue, lightly freckled or shot through with pyrite spider webs of gold and black.
Martin Colbaugh, owner-operator of Colbaugh Processing in Golden Valley, Arizona, displays examples from around the world in his shop, which is located northwest of Kingman just off U.S. Route 93.
"There's some color of turquoise, some type, that will appeal to almost everybody. And the nice thing about it is, you pick that piece of turquoise up, there's never going to be another one exactly like it to match up," he said.
Colbaugh Processing owns the mining concession for Turquoise Mountain at the Mineral Park Mine. Located in the Cerbat Mountains 14 miles northwest of Kingman, Mineral Park is an open pit copper mine that produces copper, molybdenum and silver.
Turquoise is composed of water, phosphate, copper and aluminum. It is typically found in arid regions, often with copper deposits in volcanic rocks, although sedimentary rocks can also contain turquoise.
The earliest known turquoise mining occurred in the Sinai Peninsula more than 5,000 years ago. Its familiar name came later, when the blue-green gem entered Europe via Turkey and acquired the Old French adjective turqueise, used to describe objects from Turkey or its dominions.
In the Southwestern United States, turquoise deposits, which always form within 100 feet of the surface and are therefore sometimes visible in exposed rock, have been mined for centuries by Native Americans.
"The Turquoise Belt starts up in Nevada, comes down, makes a little southeastern turn, comes into Arizona. And so, we're right there in that turn. Then it goes straight down in through Arizona and down into Mexico," said Colbaugh.
Monty Nichols, who owned and operated the Sleeping Beauty mine in Globe for a quarter century, helped Colbaugh get his business off the ground. But the Colbaughs have mined turquoise in Mineral Park for generations.
"In 1962, my grandfather was the first one there to mine," said Colbaugh.
From Muck To Magnificence
Today, what began as a low-slung brick-and-stucco building has grown to include two giant metal Quonset huts where employees sort buckets of stone by color and quality.
Pure turquoise is tough, measuring a 5 to 6 on the near-logarithmic Mohs hardness scale of one (talc) to 10 (diamond), but it also occurs in an assortment of chalkier and more porous grades. To preserve color and cohesion, suppliers sometimes stabilize the stone, swapping its water content for an optically clear plastic such as epoxy.
Stabilization differs from color enhancement or dyeing in that it does not artificially change the stone's color.
"[It] does not alter anything; if it's green on one end of the stone and blue on the other — it just brings out what's in that stone," said Colbaugh.
Still, many collectors prefer natural turquoise; it is but one of the many aspects of this nodular, waxy hodgepodge of hues and materials that reflects personal preference.
"Sometimes we'll look at something that I consider pretty low-grade, and they'll look at that — it is the most beautiful piece of turquoise they have ever seen," said Colbaugh.
Colbaugh Processing works with both natural and stabilized turquoise, through all stages or processing — from mucking it out of the ground to tumbling, grinding, polishing, cutting and setting into jewelry.
But it is mainly a wholesale operation. Although its showroom provides an ample selection for walk-ins, jewelers and artists to choose from, the company mainly sells to supply stores, catalog companies and markets like QVC and Home Shopping Network.
Tracing Turquoise's Ancient Origins
Archaeologist Saul Hedquist now works for Logan Simpson, a cultural resources consulting firm, but he was a doctoral student at University of Arizona (UA) when he grew interested in studying ancient turquoise mining.
As Hedquist explained, many mysteries remain regarding the two dozen or more known pre-Hispanic turquoise mines in the American Southwest, many of them in Arizona.
"One of my questions was, were they getting turquoise from similar places, even though they had different backgrounds?"
For his dissertation work, Hedquist performed an in-depth survey of Canyon Creek, a 14th century turquoise source located on today's Fort Apache Indian Reservation.
"The White Mountain Apache Tribe was critical to all this. I mean, they provided not only permission to be there on their lands, but also they were a part of the work — they were out there in the field with us," said Hedquist.
In addition to locating a new site where Ancient Puebloans dug turquoise at the mine, Hedquist found evidence that the area was far more active than archaeologists had previously thought. But how far did its influence reach?
To find out, Hedquist gathered 94 artifacts from 12 pre-Hispanic Ancestral Pueblo settlements in eastern Arizona, intending to trace the turquoise back to its origins.
Enter fellow UA alum, geochemist Alyson Thibodeau. As a graduate student looking for geochemistry projects, Thibodeau had grown interested in turquoise due to its significance in that archaeological record of the Southwest.
"I kept hearing archaeologists tell me that people wanted to know where turquoise came from, that they were interested in a method to trace the source of archaeological turquoise," Thibodeau said.
Thibodeau, now an assistant professor of Earth sciences at Dickinson College in Carlisle, Pennsylvania, had found the answer by adapting a technique called isotope geochemistry to map turquoise to its source rock.
The technique involves measuring telltale ratios of certain isotopes — versions of elements with the same number of protons but different numbers of neutrons — and matching them to a known reference rock.
Turquoise forms when water dissolves copper deposits and nearby rock, leaching out copper, phosphate and aluminum. But the process also sweeps in a lot of odds and ends, such as the strontium and lead isotopes that Thibodeau needed for her technique.
"I call it sometimes 'the garbage can mineral,' like, you know, it's full of so many impurities," she said.
Rock's chemical composition is not set in stone. Over time, unstable isotopes break down into other substances: Through radioactive decay, uranium becomes lead; potassium gives rise to argon. Because this process follows a known schedule and sequence, geologists can sometimes use it to date the rock — or, in this case, provide a kind of fingerprint.
"The turquoise ends up kind of just acquiring the signature of the rocks that it forms in," said Thibodeau.
Isotope geochemistry provides more reliable data than its predecessor, trace elements analysis, which involved assaying amounts of particular elements in turquoise samples and matching them to previously sourced turquoise.
The problem with trace elements analysis is that turquoise's makeup can change, even within a single vein. Moreover, a given mine might comprise several pits spread miles apart, each turning out turquoise with slightly different compositions. Conversely, turquoise from two different regions might share a similar composition.
In other words, trace elements analysis provided less of a "fingerprint" and more of a "blood type" — good enough to narrow the field of suspects, but vague enough to limit valid inferences.
"You need a tracer that will basically give a similar answer no matter where you are," said Thibodeau.
Thibodeau explained that, because these signatures vary from region to region, even if isotopic analysis cannot tie turquoise to its source, it can at least narrow the list of candidates.
"Southeastern Arizona is different from northwestern Arizona, and both those regions are different from central New Mexico and central Colorado."
"It was way, way bigger than was previously thought," said Hedquist.
Hedquist also consulted Hopi and Zuni elders to understand their cultural relationship with turquoise.
"Some of the traditions that Hopi and Zuni have about turquoise and where it came from in the past matches what we see in the geochemistry in doing the provenance work. It's amazing."
Turquoise In Context
Every mine — whether Canyon Creek or the Ithaca Peak mine where Colbaugh's grandfather began in 1962 — has its heyday, bookended by discovery and abandonment. Today, many Southwestern sources have been exhausted or priced out of business.
Kingman is one of the last full-time mines in the United States and the only large-scale commercial Arizona mine still producing.
"Everybody's not working right now because world prices are so low, they can't mine it economically," said Colbaugh.
Yet the legacy of the mines lives on in market bazaars, cultural ties and the work of archaeologists who trace turquoise's path like a blue-green vein through Arizona's past.