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Untold Arizona: The Ancient Ground Stones Of Arizona

When people think of Bisbee, Arizona, the mining industry is likely top of mind.

Diana Grege is one of the volunteers who keep the Bisbee Restoration Museum alive.

"This building was built in 1908. It was restored after a fire. So the original building was 1902, designed by an architect in El Paso," Grege said.

While a substantive amount of the museum is devoted to mining, it wasn’t the precious mineral history preserved here that makes an impression.

I first visited last December and recently returned to find out more about some ancient rocks on display called metates.

These metates, commonly referred to as ground stones by archaeologists, at first seem out of place compared to other artifacts: dolls and clothing from the early 1900s, taxidermy of a two-headed calf, World War II memorabilia, mining implements, a copper diploma from Bisbee High School, an early personal computer and familiar kitchens, cocinas from yesteryear. But before this was a record of history, its contents, including the metates were in disarray

"When I started here, these were scattered all over the building," Grege said. "They were stuck behind things, under things. And, finally, I found out what they were."

The first time I saw similar-looking artifacts was while I lived in the Marianas on the Micronesian island of Guam in the Western Pacific.

And, while the word metate is known by many on Guam because of Spanish colonization on island, the indigenous Chamorro culture use an Austronesian word, Lusong. Many of these Lusong are visible in the ancient village of Pågat.

Is There More To Ground Stones?

Diana Grege discusses ground stones



Domenica Tolentino is director of the Guam Museum. We began our conversation with a customary Chamorro greeting.

“Håfa adai. Good morning.”

I asked Tolentino to define the word Lusong.

"The term itself just means a grinding surface. But, when we talk about Lusong on Guam in reference to ancient Chamorro culture, it’s usually in reference to the semi-portable large boulder," Tolentino said.

"They vary in size, but the most common size that I’ve seen, at least among our collection, is a circular rock surface of about a foot in diameter. And then, the pounding area goes in about about six inches or seven inches deep."

Lusong are still used on Guam.

"Today, our healers use Lusong to prepare åmot, or traditional medicine," said Victoria-Lola Leon Guerrero, managing editor of the University of Guam Press. 

Leon Guerrero said Lusong maintain significant traditional weight today because of stories passed down over generations of Pacific Islanders living on Guam.

What Are Lusongs?

Victoria-Lola Leon Guerrero shares more about lusongs


Oral Traditions

"In oral tradition, it’s something that we’ve always been told is a sacred item, is an item to be respected. It’s one of those things that’s just sort of always visually in your mind when you picture the tools that our ancestor used," Leon Guerrero said.

She also said archaeologists have dated use of stone Lusong by the Chamorro culture for about 1,000 years, but there was likely a wooden precursor.

Back in Bisbee at the Restoration Museum, Grege describes how the ground stones on display were utilized, depending upon the shape and characteristic indentations.

“The ones with the deepest holes were used for the hardest grains. And then, the ones that are less indented were for corn and beans and things that were brittle,” said Grege.

The metates in the museum have a variety of unverified dates of use and origin. And that makes volunteers like Grege cautious of her own intuition as a tool for discussion.

"When I first saw them, I was a water person myself, and I thought it was from water erosion — that they were underneath a trickle or a waterfall," she said.

“In oral tradition, it’s something that we’ve always been told is a sacred item, an item to be respected.” — Victoria-Lola Leon Guerrero

Ground Stone Terminology

This part of the story begins in Tucson, where I met Jenny Adams at Desert Archaeology, a woman-owned company. Adams is a research archaeologist and an expert on ground stones.

And when we call these ground stones, just for layman’s terms, is that because these were things that were simply placed on the ground, and you didn’t find them in a mountainous region? What’s the terminology?

"That’s exactly — when I first started school, I thought, well, they’re all ground stone. Look! They’re all found on the ground. But no, it has to do more with the way things are shaped by grinding, or that they were used to grind things." Adams said. "It’s really a construct by archaeologists. If you were to say 'ground stone' to another archaeologist, they would know exactly what you’re talking about."

For a person who’s never seen these, but maybe has used a mortar and pestle in the kitchen, a small version of a ground stone, would that be a fair comparison?

"That’s very fair. Mortars and pestles go all the way back into several thousand years B.C.E. And, some chefs will tell you the best way to do your spices is to grind them up in those stone mortar and pestle," said Adams.

And that familiar word is tossed out in our conversation, surrounded by stones of all types and microscopes to examine their deeper context.

Is It Like A Mortar And Pestle?

Victoria-Lola Leon Guerrero shares more about lusongs


Metate And Manos

"The other terms for tools to work food are manos and metates. Mano is Spanish for hand. Metates is a different origin word," Adams explains. "It comes from the Aztech."

Adams said she’s skeptical of the older dates displayed in pictures of the Bisbee Restoration Museum ground stones. Admittedly, photos alone put her at the disadvantage of not being able to sample them herself.

So, how does one date the use of a ground stone that may be millions of years old?

The answer would take me back to the Valley where I caught up with Craig Fertelmes. He’s senior archaeologist with Logan Simpson, an environmental consulting and cultural resources firm in Tempe.

Fertelmes said his work with the Gila River Indian Community helped him identify the geochemistry of many ground stones in the Phoenix basin.

"We can analyze with a technique called X-ray fluorescence spectrometry, which produces a geochemical signature. From that, we can compare it to the reference database and reconstruct where ground stone from a prehistoric context derived. What you find is that social relationships among villages were pretty complex and people were acquiring stone from multiple resource locales," Fertelmes said.

How Do You Determine Ground Stones As Artifacts?

Jenny Adams breaks down ground stones


Older Ways

Fertelmes referred me to Leora Newman. She and her family have been part of the Gila River Indian Community for many generations.

We discussed metates and the fondness of older ways.

"What I remember is that my aunt would grind corn and wheat on those and she would make chili stew with the chili pods she would grind. I was just a little girl then," she said.

Newman said the metate her ancestor used was outside the kitchen window and approximately 15 by 12 inches. I was curious what other characteristics she could remember such as striations or indentations.

"Yeah, an indentation in the middle part from them using it all the time," Newman said.

Newman’s daughter, Linda Morgan, also remembers stories of ground stones.

"My grandfather also used to talk about the manos and metates because we had some in our yard, three of them I think in our possession at our house," she said. "We always kept them outside because that’s just kind of where they belonged. My mom didn’t use it to prepare food. I didn’t use it to prepare food. So, that tradition for our family ended in the late '40s."

And while such large ground stones may not be practical in the modern era of densely-packed cities, smaller metate and mano-inspired mortars and pestles abound in home and restaurant cocinas.

Can You Tell When A Ground Stone Was Used?

Tessa Branyan explains ground stone artifacts


For Diana Grege at the Bisbee Restoration Museum, using such tools makes a better sauce.

"When you think about mole, there’s nothing like a fresh mole sauce compared to a jar," Grege said.

And while some stories — like verifying the dates of use for the ground stones in the museum — might go unanswered, it’s not for a lack of telling their story.

Tom Maxedon was the host of KJZZ’s Weekend Edition from 2017 to 2024.