The dark colorations in this agate were formed by silica and water.
This agate was a bit tricky to spot, but holding it up to the light, banding can be seen through the translucent parts of the rock.
This is a good example of the red and orange colors caused by iron oxide.
As a kid I remember taking long walks with my grandma through the prairie, and she would go along picking agates. As an adult, I learned that Montana agates are some of the most unique and sought-after agates in the world, bringing people to our area from all over. Still, there are many people in the area that have never tried the past-time that draws so many visitors, and so I decided to give it a go.
It's easy to spot an agate, all cleaned up and gleaming in the sun, however deciphering them amid hundreds of other rocks is a challenge, and my childhood memories are a little blurry, so I contacted Tina Bartelson with Harmon's Agate & Silver Shop & Museum in Savage.
On a hot summer evening, she was kind enough to give me a crash course, and we headed to Elk Island. Being the daughter of Tom and Cheryl Harmon, owners of Harmon's Agate & Silver Shop & Museum, Bartelson has been agate hunting for as long as she can remember and immediately starts picking them out of the gravel along the river banks.
August through October is agate hunting season along the Yellowstone River, which recedes and exposes the rocks along its banks. Montana agates are unique because they have all the qualities of every other agate in the world including banding, unique colorations, and dendrites; they are formed with water, silica, lava, manganese, and sediments and the key to finding them is to look for a rock that has some translucent part to it.
An agate's beauty, after it's been cut and polished, is the patterns and pictures that have formed within it. Silica and water create the black coloration, manganese is responsible for the white, and reds and oranges are the result of iron oxide.
As we hunt, Bartelson explains that it's a cost effective, family-friendly hobby, that gives people a good reason to spend a day outdoors, along the river. A gardening spade, backpack to bring home your haul, along with water and sunscreen are really the only equipment you need to get started. Seven Sisters, Elk Island, Intake, and the MDU bridge are a few places that are good for agate hunting.
As we go, I realize that my eye isn't as sharp as I might've hoped, presenting several findings to her that she tells me are very pretty rocks, but not agates. The best way to tell is to rinse them in the river and hold them up to the sun to determine if they're translucent. We even find some petrified wood and quartz.
"People can bring what they find into the shop and I can tell them for sure if they've got an agate. A lot of people bring in quartz because it's sort of translucent, but it's also usually smooth. Agates are more dimpled," she explains.
They can be used to make jewelry, wind chimes, lamps and much more, though it takes a diamond blade to cut them because they have a #7 hardness. In my case, they will simply be a unique and beautiful addition to landscaping.
For more information about how to find them or what you've found, call the shop at 406-776-2373 or visit them at 10690 Highway 16 in Savage, MT, 9:00am to 4:00pm, Monday through Friday, or weekends by appointment.
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