I'm not sure what I'm looking at, but it's interesting. It isn't impossible to come across portable petroglyphs in our region. Of course, some are engraved on decorative artifacts, like pendants. Some are seen on tools. For instance, the turtle seen as #11 in this illustration is engraved atop an abrading stone. And #9 is a slate knife with some type of critter engraved on it. If you double click the photo, you'll see the artifacts better......
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You can see some of these at the Massachusetts Archaeological Society's Robbins Museum in Middleborough, Ma. The turtle abrading stone is at the top in this photograph:
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#6 in the above illustration is seen on the right side of this photo. It was found at the famous Wapanucket site in southeastern Ma. Hard to see the tally marks in this photo taken through glass:
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Finally here is a portable petroglyph from my own collection. I would not take my speculation about this one too seriously. It's just me speculating. The fact is the particular design, a crosshatch, is one of the most common design elements in North American petroglyphs. For that matter, the world. So it could be Paleo, but it could be Woodland in age as well. I have no way of really knowing. I disagree with my colleague, Ed Lenik, who felt it was a net weight. As far as I'm concerned, it's an unmodified cobble of quartzite, a true portable petroglyph:
http://www.treasurenet.com/forums/north-american-indian-artifacts/586010-portable-petroglyph.html