Indian Grinding Stone??

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Grinding stone?

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a full view of stone

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i have found several points in the area, both sugar quartz and gray flint, the sight is only abount a mile from a large river, the Ogeechee and there is a creek oabout 30' from the rock. Would it be worth while to screen the dirt around the rock for artifacts and how should deep should i go? thanks ,Craig

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These were found in the area of the rock where we cleared off for a cabin. Why so many different types and materials??