by Dion Stewart
Although it was the second day of spring, the story of our field trip to collect beautifully banded green, brown, red, and yellow jasper (photo to right) in Northwestern Georgia began nearly 500 million years ago. Back then, in Ordovician time, Georgia was covered by an inland sea that deposited mostly calcite with some silica ooze that hardened to form scattered chert nodules in a limestone and dolostone that today is known as the Knox Formation.
About 250 million years ago when the Appalachian Mountains formed, these rocks were cracked and hot watery solutions dissolved the chert; and the silica rich fluids flowed through the cracks at the crest of the fold to deposit the layers of jasper that we found on the trip. The microscopic quartz in these layers was colored by trace amounts of iron and manganese to give mostly red and green layers. In many places the cracks in the ground were not completely filled with minerals and here quartz crystals lined the cavities from small layers of green druzy to a few large red quartz crystals that lined larger vugs (photo to left).
The trip followed logging roads that went right up the middle of the cracked region of the folded anticline and you did not have to hike a lick … you just stopped the car and looked in the road (photo to right) to find the banded jaspers. Jasper made out of quartz is very resistant to erosions so every time the road went up a steeper slope, we stopped the cars and the bands were right on the surface with jasper chunks everywhere. Participants all got a very full bucket plus a few yard rocks to add to their collection.
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