We had a great day collecting on our June 1st trip to our new site on private land near Menlo, GA. We visited two sites that were only a mile apart, both areas are part of the Fort Payne Chert Formation that was deposited on the sea floor about 350 million years ago.
The first area we visited yielded some great pieces of jasper, chert and agate with banding in greens, peaches, and browns. We also found a lot of black and brown ooltic material (see below). One very lucky rockhound found a beautiful flint arrowhead in the gravel at the beginning of the road.
Our second collection area had pink and burgundy banding as well as green and others colors. One participant found a beautiful boulder of a crazy lace type agate which he extracted as a single large piece to take home. He also shared some pieces of the original boulder with his fellow rockhounds.
If you missed this great trip be sure to put it on next year’s calendar, we’re going back! It looks like we can schedule a day in April when it’s a bit cooler!
WHAT ARE OOLITES?
Oolites are tiny structures found in some sedimentary rocks that formed in an agitated marine environment. A single oolite (called an ooid) is a sand-sized, zoned spherical structure. An ooid always has a quartz grain or carbonate fragment in its center. An ooid is tossed around by the turbulent wave action in shallow marine environments.
As the ooid is rolled around on the seabed, it accumulates concentric layers of chemically precipitated calcite (calcium carbonate) from the sea water around its sand sized nucleus. All oolites originally form in limestone, however as seen in our site near Menlo, when groundwater flowing through the rock has lots of dissolved silicon, the calcite in the oolites can be turned into quartz, as limestone is turned into chert. When turned into quartz, the oolites can be polished and the concentric layers can easily be seen when examined with a hand lens. Oolite are less than 2 mm in size.
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