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Dryhead Agates
Bighorn & Pryor Mt Range, Montana (near Wyoming border)
  The Dryhead Agates were named after many bison skulls found near the site. That was where the Native Americans were said to run the bisons over the cliff, killing many of them, and then arranging the bison skulls in ceremonial manner. The agates come in form of dark colored concretion nodules found in the shale(mudstone) bed, and because of overlaying hard limestone bed, it takes some hard digging to obtain the nodules and only a small percentage of the nodules was said to be of any good. It used to be a fee collecting site in 1970s, and there had been changes in the ownership of the site. There was some mining activities using the heavy machines. Currently, it appears that the owners of the area is not interested in allowing anyone to dig for the agates. There are several other deposits including one in-sited in a Native American Reserve so any diggings are not permitted there.
   
The typical color of the Dryhead agates are brownish orange, but they can also come in the yellow, red, pink, gray, lavender and white colors. The color combo of orange, red, pink and white is the most desirable. It's typical for the Dryhead agates to contain interlaying of quartz and agate which apparently supports a concept that the agates may have been formed by successive layering in respect to the wet and dry seasons.  The Dryhead agates have an interesting form of fluorescence. The quartz bands of the orange Dryhead agates (without pink/white cores) strongly fluoresce green, hence, the glowing neon green "contour lines" against dark non fluorescing bands under ultraviolet light.
For further reading, please refer to John Hurst's Book:
Dryhead Agate: An Inside Look at History, Mining and Natural Beauty of Agates from Montana's Dryhead Region.


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rough
Rough Appearance: Disc-like gray nodules sometimes with orange agate showing (dead-giveaway)
Agates are typically orange colored, sometimes come with white, pink and yellow. Always interlaying with quartz bands.


agate
agate agate



agate agate agate

Unusual feature.
Apparently 3/4 filled with solution.

agate agate agate
Amethyst center


agate agate agate

Interesting colors

agate agate agate
Interesting structure




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