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Andrew Alden

Argentinian Adzeheads

By April 9, 2013

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basalt toolsAt least, that's what they look like to me. A reader submitted this photo to the "My Igneous Rock" page thinking that they were crystals. Yes, they're faceted, but these objects have every appearance of being stone tools. Have a look at the full-size shot.

Stone tools
About basalt
Gallery of obsidian
Richard Desomme photo, all rights reserved


April 9, 2013 at 10:55 pm
(1) Wayne Campbell says:

Andrew, I don’t think they are tools per se, in that a tool maker would have taken the trouble to refine the shape using various flaking methods. They also do not look stressed by use.But they could very well be flakes struck from a core put aside for further refinement or for export. I often wondered about the commerce around stone tools. Could these flakes
have been struck from a core in order to export from an area of abundant tool grade obsidian for sale to another region, with the final shape customized by the buyer, thus reducing the hauling weight for the seller?

April 11, 2013 at 3:27 pm
(2) Wayne Campbell says:

On closer look, I now think you are correct Andrew. Ground hand axes made from fine grained basalt. I have a couple just like them in my collection. Cheers!

April 15, 2013 at 9:08 am
(3) Ann Archaeo says:

One looks like to be a beveled adze (the tool on the upper left), the other two could be “blanks” from a quarry. It’s difficult to tell from the photograph. Some edges appear to be worked. Basalt has been used to make tools, esp. in Canada where basalt is plentiful (it can be really hard). Other rock material that may be used for tools: granite, obsidian, sugar quartz, chert, and flint.

(The above comment from an RPA)

April 15, 2013 at 10:34 am
(4) Ralph J says:

Could the original stones be “ventifacts” that were subsequently reshaped into tools? I agree that some edges appear to be worked, but other edges and the shape of the stones look strikingly similar to ventifacts. If you do a Web search of images of ventifacts, you’ll see some stones that look just like your image (without the refined edges)

April 15, 2013 at 11:33 am
(5) Amy Lamborg says:

Hello Andrew! You are the most wonderful geology educator ever! Thank you SO much for your awesome About.com geology site. I will say, though, that I don’t think these possible stone tools would be classified as basalt. I think they are closer to obsidian. Obsidian would naturally flake with the kinds of angles shown in the pics, and the guy who found them noted that they sound nice when clinked together–I think that suggests they are glassy. In addition, the place they were found has lots of scoria cones; to me this also suggest obsidian is a possibility. The obsidian isn’t clear, but that’s OK…I think lots of obsidian is opaque. As to whether they are tools or not, I don’t know. It could be that those natural fracture angles make it *appear* as though it’s been worked; but I do see what you mean on some of the edges.

April 15, 2013 at 4:50 pm
(6) Geology Guide says:

Amy, I’m sure you’re correct. The odds are that a stone of this quality is more likely to be whinstone (very fine grained basalt/andesite) or rhyolite, something closer to obsidian, than your run-of-the-mill basalt.

April 15, 2013 at 7:00 pm
(7) Geology Guide says:

Another reader has stated that these are artificially worked stones, but it’s the local village kids who do it, taking naturally formed ventifacts (dreikanter) and chipping edges on them. So if he’s right, everyone commenting is right!

April 16, 2013 at 9:26 pm
(8) Don MacLean says:

Andrew…I believe these to be “dreikanters”. I have some very similar from the Sahara. They are faceted on sides that conform to seasonal winds, with a sandblasting effect. I admit that mine are limestone, perhaps more easily worked.

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