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This excerpt from "A Revelation" published
in the 2022 Central States Archaeological Societies 2022
October Journal
Read the complete column in the Central States
Archaeological Societies 2022
October Journal which can be purchased on-line after March 2023
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If you’ve ever had one of those “ah-ha moments,” then
you’ll relate to this article. I have been collecting for several years
and along the way I have acquired a number of collections. Normally, I obtain
several hundred pieces to get maybe 10 worth showing off. In 2018, a close
friend asked me to come look at a small group of artifacts he wanted to let
go. What he had were several pestles, some pottery fragments, pottery disks
and a jar of mostly field-grade points. I didn’t have any pestles at
the time, so I agreed to take the lot from him.
I brought the pieces home, went through them and decided which ones to
add to frames and what to just store in a cabinet I use. The two pestles
were placed in my hardstone frame and there they sat for a while. Down the
road I decided to start to educate myself about the types and ages of what
I owned. I did so by buying books at every chance I got and reading constantly
about the cultures and what life was like for Native Americans across the
vast time they occupied this continent alone.
|
This excerpt from "A Revelation" published
in the 2022 Central States Archaeological Societies 2022
October Journal
Read the complete column in the Central States
Archaeological Societies 2022
October Journal which can be purchased on-line after March 2023
|
|
|
|
|
As I started to learn about the manufacturing of hardstone implements, I
hit on something odd. The pestles I had purchased didn’t fit the peck
and grinding theory. They were shaped for sure and likely through pecking.
But these had a shell on the outside which was commonly referred to as hematite
by collectors and at the core were obviously a different type of stone (I
had taken geology in college but ended up in I/T, which led me to a career
in software development and project management. I currently work for the
Department of Defense at Fort Knox).
I was determined to learn more about what I was looking at and what was
required to make these pieces. I first had to determine the actual material.
As stated earlier, the outer shell was always described as hematite and after
some simple testing, I determined that the cores were made from limonite.
Both hematite and limonite are common iron ores found here in North America.
Here’s the thing that puzzled me. How did the Native Americans get
a hematite shell on the outside of a limonite pestle?
This is the point of revelation. The chemical formula for limonite is FeO(OH)-nH2O.
That’s iron with an attached water molecule. Hematite’s chemical
formula is Fe2 O3. That’s also iron, but without the water molecule.
The light went on. The shell wasn’t hematite. It was crudely smelted
iron. The Native Americans must have somehow figured out that if they heated
the limonite enough, they could remove the water molecule and leave behind
only iron, which would easily be mistaken for hematite.
At this point I started searching for references to these artifacts to see
if anyone had already made this connection. I found nothing. This is where
things got fun. I’m a project manager, not a scientist, geologist,
anthropologist or an archeologist. To prove my theory, I’d need to
be all four. I first had to learn about the process to make iron from limonite.
Limonite can be converted to iron through the process of heating. It is crushed,
heated and the impurities are skimmed off, leaving a semi-pure iron that
can then be heated and beaten to shape or melted and poured into molds.
It has been used for millennia to produce iron all over the world. There
is only limited evidence that Native Americans knew anything of metallurgy
(Ref. 1). Examples would be native copper from the Great Lakes region and
gold from Mesoamerica. If true, this would be the first and only example
of Native Americans crudely smelting iron during the pre-Columbian period
of North American occupation.
The temperature required to begin driving off the water molecule is somewhere
between 250-350 degrees Celsius (Ref. 2). A wood fire burns at approximately
800-950 degrees Celsius (Ref. 3). Modern smelting uses much higher temperatures,
but that is to expedite the process. This means that it is entirely possible
for a piece of limonite to be converted to what would appear for all intents
and purposes to be hematite by heating it for a period with a wood fire.
So, the theory is possible.
The question for me was why they would bother. This is part of my hypothesis.
Limonite is a relatively soft stone with a hardness on the Mohs scale of
4-5.5. In contrast, a piece of granite has a hardness of 6-7 on the Mohs
scale depending on the quartz content. On its own, limonite wouldn’t
make a very good tool. It would wear down easily. I think at some point a
Native American used a piece of limonite he found to build a fire ring.
He noticed after a period that the side facing the fire had transformed
into something different. He found that hard surface useful, and they eventually
determined they could shape the soft stone into a tool and then through baking
in the fire, turn it into a useful tool for grinding and chopping. It seems
like it would be easier than all of that pecking of much harder rocks. There’s
no way to prove this, but it seems logical. Armed with this knowledge I decided
to ...
