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Discussion Of Burlington Chert
Ahnlaashock:
I am a beginner, even tho I am an experienced lapidary. I started trying to learn how to make simple tools, the way they did, from available local resources. I knew there was a local chert in sizable pieces, and that has since been identified as Burlington.
Everyone says Burlington, like it means one thing. Well, that isn't how it is here. I have brown grainy material, all the way to agate like translucent material. Heck, I even have a piece with a barber pole swirl. I have several grades of Burlington, that do not require any kind of treatment to knap well and easily. The best is almost as easy to work as good true flint, and only obsidian has been easier to work for me.
I can post photos of the various grades I have so far encountered, if needed.
The very best working material so far, is a glassy banded/swirly pure white to gray material. It compares very well with many lapidary materials. It even fractures to a smooth shiny surface, time after time. You can push flakes on it raw with a pressure tool. Unfortunately, the piece I found was float, and badly fractured. The material appears in the creek over a wide area, but it is all in small pieces, about golf ball size. It patinas white or banded. The piece I worked was from near the top of a ridge, in a very steep valley. The top layer was this pure material, but the other parts of the same core were much courser grained and hard to work even with hammer stones. The finer material compares favorably with many agates or fine lapidary materials, and would make a fine polished piece also. So far, it is not translucent, but instead is of a solid color, although it may be swirled or banded. Many of the fine grained smaller pieces appear to be a solid gray inside if struck, even if they were banded in the patina. Some of this material is translucent. If you are used to working with tough stone, you will hit this one too hard in the beginning. Brushing up the edges makes flakes rain like crazy, it can be worked all the way to pressure stage, using antler billets, and one of my billets is a whitetail tine. Both ends can be swung to work the better material. Oddly enough, the tine billet tends to knock almost hollow ground edges when used.
I also found limited quantities of a darker gray material that does things like produce three inch flat flakes, but so far, that supply is very limited.
I even found a version that has sparkles all throughout the material, making it look like it has glitter inside the stone. It works okay, but the edges are not as sharp as the more solid material. It appears to be small crystals locked together in a matrix when you start to work it. For jewelry use, it might make perfect points, but for actual use, it isn't sharp enough or tough enough.
So far, here in northern Jefferson County, the material is mostly the gray stuff that leaves a grainy pebbled surface on flake scars. I found one deposit of a much finer grained material in large pieces. I posted a picture of it in the Jefferson County Chert thread. It is also not translucent. There is a much finer grained gray material that is hidden under a variety of patinas that is common here also. It is very hard to work without treatment of some kind. Some of this material is translucent. It is just hard and tough.
The much better material I was talking about, is from Washington County for the most part. I have found a white material that may or may not be banded, and may or may not be workable there. The very best being this incredible material I have been bragging about, and the worst is thin layers with layers of concrete in between each.
There is a gray material found in larger pieces, with the patina we recognize as Meramec cobble here in this area. It is often in layers also, and is often badly twisted and uneven. Good layers can be worked pretty easy, but I don't know about flaking with pressure or not. Why one forms the brown patina, and the other forms a white or banded patina, is not evident from the material itself. Inside, a flake from each can be confused with each other.
So, when you say Burlington, as so many do, are you describing one certain type of Burlington, or are you discussing it in general? I am not sure the spread of material I have found, even in this short time period of searching, fits under one name or variety.
Describe what you call Burlington, please!
Dalton Knapper:
There could be other rock present besides Burlington Chert. What you have to realize is that you are talking about rock formations within a geological area that could be mixed with other eroded strata from earlier periods unless you find the rock in a formation that can be identified. Being familiar with lapidary, you should know that Jade for example can be quite varied. Well, so can chert. Perhaps you are finding different rocks and some Burlington as well.
Novaculite can be anything from a sandstone like texture (which the whetstone industry loves) to something that looks much like a chalcedony and is translucent. It's all about geology.
This shows some variety in Burlington: http://www.uiowa.edu/~osa/lithics/drawers/OutOfState/DrawerLGImages/Drawer8Images.html
Ahnlaashock:
While there may be the odd rock that is not Burlington, most of it is. I have seen examples of the various types or grades being part of the same piece, as with the best I have found. It was the top layer, and what was under it would have been like working quartzite. I spent the last two days spalling and removing flaw from the pieces I collected here close to home.
It runs from very course, almost quartzite textured, or even larger crystals that sparkle in some samples, to glassy and translucent. From solid color to banded to layered. From pure white, to dark gray.
I was watching a video, and the person said that the stone they were working, was a lot like working Burlington. That kind of threw me, since what that means, is you pick up each piece and see how hard you have to hit this specimen. The strikes used to spall the last piece, might completely shatter this chunk, or may not even bother it at all.
Making blade or flake functional tools is no problem, but i still can not push a flake at all. That is why I am going to heat treat a batch. I am keeping plenty as is. I still plan to learn how to work it fully raw also. I took a picture of the stuff I am cleaning up right now, with flakes of the other grades mixed in. Heck, there is even one of my pitiful blade points, or a partial anyway. It sits on similar material. It is all the same material, and seems to basically be different grades. The glassy chunks might have been heated in nature, but they are a class way above any of the others. I just have not yet found large chunks of that material that is not already fractured badly. In the creek, it averages about golf ball size chunks. I did not have any of the brown handy. The big spall is right at 6 inches.
iowabow:
Go to the university of Iowa and down load the geological survey. I live just outside of Burlington Iowa and the formation is named after this area. That survey will explain in detail what Burlington is.
iowabow:
Another link https://gsa.confex.com/gsa/2002NC/finalprogram/abstract_32594.htm
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