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Copper Mask

So I was out fossil hunting last weekend when I happened upon something....strange.


I was digging around the wash of a small waterfall and stream when I happened upon this mask. I figured it would be a great time to look for fossils, since a heavy rain the night before would have washed away a lot of the sediment. Its two eyes were peeking out from the muddy bank. It was very creepy looking.


So I picked it up and put it into my backpack, and forgot about it until today.


I have no idea what to make of it. Maybe someone tossed an old art project down there. Maybe someone stole it off a statue. I really have no idea.


It looks like it's been down there for a while. The forehead design, mouth and one of the ear/strap holes have been sealed shut by thinly melted copper, and sand concretions There are still some small holes in them. There's quite a bit of sand concretions on the face of the mask too.


I took it to work and hit it with our XRF instrument, and it's made of 98% copper about 1.5% Silicon and about .7 Manganese. Yeah, it doesn't add up, but if you've used an XRF, you know it's touchy.


Anyone have any idea what this is?



From one of the curators at the Science Museum of Minnesota:

I did finally have the time to give your mask a good examination with a colleague of mine.

The mask is certainly a modern creation. As you had expected, perhaps someone's art project. Still, what an interesting find while out collecting fossils!


Here are my thoughts and speculations:


We took a series of XRF readings. The material is mostly copper. Between 93 and 98%. There is some silver in the mix, suggesting that it may include some native copper. However, there is also a higher than usual Zn content for native copper. Usually there is not Zn in native copper from the upper Midwest. There are also percentages of Mn and Al, which doesn't occur naturally in copper. Manganese and aluminum was not added to copper until the 20th century. Alloys that include Mn and Al were created during the war efforts to reduce corrosion. So, the mask is a cocktail of probably scrap copper and perhaps some native copper.


Stylistically, it doesn't resemble anything I've seen archaeologically from the upper Midwest. However, it is interesting that it was clearly created to look rough and old. The calcite deposits were probably added to give it a look of natural long-term corrosion. Probably lime concrete. The crystallization is spotty and undeveloped.


Technologically, the mask was definitely cast. The metal was heated beyond its melting point (over 1900F), leaving drips and bubbles. This is not consistent with aboriginal copper working practices, where copper was hammered and annealed.


I don't think the mask could have been buried in fossiliferous gravels in the ravine for very long. Examining the mask under UV light revealed some very fragile wax along one of the edges. Some of it dislodged with the slightest touch with a probe. So, that is unlikely to have survived on the mask for long, especially in an active environment like that ravine. The mask may have been left as little as a day or two before you found it.


Still, it is yet another great example of a very strange thing left behind in an odd place. Like I said, probably someone's high school or college art project. How it got in the bottom of the ravine is anyone's guess. Great conversation piece.


That rings true for what I thought. I was in that ravine literally the week before and it wasn't there then. Anyway, it's still a neat conversation piece to hang up in my shop or garage.

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Taken on July 21, 2010