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"Chipped and Ground" Calcareous Chert Adze

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  • "Chipped and Ground" Calcareous Chert Adze

    In a self-published, local archeology book, a much respected collector and amatuer archeologist refers to an adze he found as made of "impure calcareous chert" that was "chipped and ground." He goes on to say the local acidic soils have leached out the calcium carbonate impurities, leaving the adze very light in weight, and light in color. I have held a similar piece found in the same area of Cayuga County, NY, and in fact, it is light as balsa wood and more 'blonde' in color than the normal gray Onondaga Chert color! Quite remarkable. It's surface looks to me like large 'chips' or 'flakes' were wacked out of it during its manufacture. It does not have the overall, smooth surface look of other adzes and celts I have seen.

    So while I can understand the "calcium carbonate impurities leached out by acidic soils" part, I'm not sure I understand the "chipped and ground chert" assertion.

    Can chert be "ground" ....like hardstone tools are "pecked and ground?" So, wet sand (....assuming this was the abrasive used....) is hard enough to grind down chert to make the bit end of an adze? I thought that the quartz component of sand and chert were of the same hardness. (Moh's = 7)

    Any clarification is appreciated!
    Last edited by Cmcramer; 09-07-2019, 08:42 AM.
    Cayuga County, NY Finger Lakes Region

  • #2
    I did respond to your email, but will repost here, now that your post comes up. There really isn't a type of chert called " calcareous chert ". Anything calcareous in nature would be from acidic water reacting on a variety of rocks and soils, leaching out the carbonate minerals in a secretion. This would harden into limestone and the calcite group of minerals. These are soft and rarely used for hardstone artifacts. Cherts are formed from the secretions of silica oozing out of rocks and soil deposits. Some larger cobbles of Onondaga chert may have a calcareous rind, but that is chipped away to get to the chert.
    On the hardness factor, pure silica will have a hardness of 7. But even being silica based, not all cherts are pure silica. The impurities in certain cherts may soften them to a hardness of 6, maybe even 5. At this point, certain chert tools may be ground smooth using sand, water, and a polishing stone. Many of the Danish and Neolithic axes, chisels, and hardstone tools are polished smooth using this process.
    The only other thing I am considering, but with out a photo, wouldn't know for sure, someone may have picked up a natural limestone rock shaped like an artifact, thinking it was an adze. We on the forum see this about every day. Natural rocks being turned into some form of artifact. Hope this helps!
    http://www.ravensrelics.com/

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    • #3
      Thanks for the discussion Guys. I don't have anything to add to what Paul has said but i do have a celt that is very light weight for the volume of rock. I'm sure this rock has been degraded while in the acidic soil for many years.

      Click image for larger version

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      Michigan Yooper
      If You Don’t Stand for Something, You’ll Fall for Anything

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      • pkfrey
        pkfrey commented
        Editing a comment
        If you break that in half, you may find a very think outer layer of a softer stone that has been deposited to the hardstone inside. It all depends on where the artifact was laying for a thousand years. Maybe under a ledge with continuous dripping water that deposited a calcium based rind, making it much lighter than it should be. But these things follow my golden rule when collecting artifacts, " There is an exception to every rule! "

    • #4
      Link to an earlier thread with comments from Painshill, Mark had used Photobucket to upload the pics. ( They are not in the thread now) Photobucket was good when it was free. Anyway most important to me is RIP Mark! We miss you Painshill too . https://forums.arrowheads.com/forum/...huge-rare-celt
      TN formerly CT Visit our store http://stores.arrowheads.com/store.p...m-Trading-Post

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      • #5
        Originally posted by pkfrey View Post
        I did respond to your email, but will repost here, now that your post comes up. There really isn't a type of chert called " calcareous chert ". Anything calcareous in nature would be from acidic water reacting on a variety of rocks and soils, leaching out the carbonate minerals in a secretion. This would harden into limestone and the calcite group of minerals. These are soft and rarely used for hardstone artifacts. Cherts are formed from the secretions of silica oozing out of rocks and soil deposits. Some larger cobbles of Onondaga chert may have a calcareous rind, but that is chipped away to get to the chert.
        On the hardness factor, pure silica will have a hardness of 7. But even being silica based, not all cherts are pure silica. The impurities in certain cherts may soften them to a hardness of 6, maybe even 5. At this point, certain chert tools may be ground smooth using sand, water, and a polishing stone. Many of the Danish and Neolithic axes, chisels, and hardstone tools are polished smooth using this process.
        The only other thing I am considering, but with out a photo, wouldn't know for sure, someone may have picked up a natural limestone rock shaped like an artifact, thinking it was an adze. We on the forum see this about every day. Natural rocks being turned into some form of artifact. Hope this helps!
        Educational and Interesting, as usual, Paul. Thanks. I will snap a couple photos when I get a chance....
        Cayuga County, NY Finger Lakes Region

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        • pkfrey
          pkfrey commented
          Editing a comment
          It's pretty much the same as what Painshill ( Roger ) said. Any type rock, hard or soft, can be decomposed by acidic rain water leaching through carbonate layers of rocks, and then a softer rock can be deposited in it's place. And Dolomite is one of the carbonate rocks. But rarely was Dolomite used for a utility piece, like an axe or adze. It's just to soft. It would be like trying to pound a nail in a 2 x 4 with a piece of chalk! These softer materials were usually confined to decorative objects, like gorgets, pendants, an occasional birdstone, etc. I'd like to see a photo of the adze your referring to.

      • #6
        I really, really like this post! I’m not sure if my following comments have anything to do with this great information, or are even related to each other, but know we have very acidic soil this area. Think this because Georgia home of red clay which gets that way from iron deposits. Farmers have hard time, and add lime to our dirt to balance acidity. We have very little chert in this county, and I take prize for picking up artifact-shaped rocks!
        Digging in GA, ‘bout a mile from the Savannah River

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        • #7
          Paul and Others - Here are 6 photos of this unusual piece. It is surely an artifact; an adze I would say. And it sure is light in weight; it feels like it's made of wood - if not balsa, then maybe pine. Very light. And the color has photographed accurately, too. The photos of the bit end show darker portions....like this rock was not homogeneous.

          I'm really curious what you think of this piece. This little, local museum collection has two of these, and as I mentioned in the OP, a renowned local collector/amatuer archeologist describes this type of artifact in his book on local artifacts. So it appears at least 3 have been discovered in our area of Cayuga County, NY. Cool, huh?!

          Thanks!
          Cayuga County, NY Finger Lakes Region

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          • #8
            That is a cool adze! It looks like there are a couple of answers that touch on what I was thinking before I saw the pictures. (Paul and Mark's answers.)

            In Kentucky you commonly see a type of tool stone (celts, adzes, etc.) called cotton rock. It starts off normally heavy, but over the years "leaches" weight and gets surprisingly soft and weak. Toss a piece in a bucket of water and it'll weight about 5 times as much after a couple of weeks. I think it's a really porous, chalky capstone for Ft Payne chert, but I could be wrong. It could also be thermally altered. Heating chalky flint really drives off a lot of water and CO2, it cuts the weight pretty significantly. I think your adze has a little of that porous chert quality to it.

            If you can get the artifact pictured wet (a couple of drops of water would do it), my guess is the moisture will absorb very quickly into the rock.
            Hong Kong, but from Indiana/Florida

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            • pkfrey
              pkfrey commented
              Editing a comment
              I think Clovisoid is about as close as you can get. There appears to be some bluish inclusions in the surface that could be chert. And if being from NY, probably Onondaga chert. From Ky/Th, Ft Payne chert. I think you have a complete cobble of low quality chert with a thick rind of softer material, possibly dolomite, or any one of the calcium rich minerals that form the outside of the cobble. The Natives however decided it was hard enough due to having some chert inclusions ( almost a geode type stone ) that they first chipped it to a uniform shape, then ground and polished it. I don't think anything leached out of it, or it would be more porous in places. And the soft material would decompose around the chert inclusions leaving those raised. They are polished over as well. The thing with this is, the native may have picked it up as a cobble, thinking it would be hard enough to use due to the interior being more chert. If it's real light, that may just mean there is more of a calcium carbonate based rind than originally thought, but they made it into an adze anyway. And, it's also possible it turned out not to work so well due it's softness, and it was discarded and not used. But it no doubt started out to be an adze. It's like a piece of soft candy with a hard center. How thick is the outside before you get to the hard center. I think this had a thicker softer rind on than initially thought. There wouldn't have been enough geologic time for that to have any calcium carbonate materials deposited, I think it just came that way by nature, but it wasn't what the native thought after he finished it. There's also the possibility that it may be a geode in form, and has a hollow center. That would be an exception, but you would have to break it open to find out. This is one that can be better analysed in had to be sure. Check and see if it's light enough to float. This one is hard to explain in a geologic context of what happened to it. Or exactly what it is.

            • Cecilia
              Cecilia commented
              Editing a comment
              You are very knowledgeable, PK. I always enjoy learning what you know.
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