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I would maybe treat this clay as red earthenware, which is how it seems  to be acting.  The aldershot clay deposit near Burlington, Ontario produces a similarly firing dark brown brick and it has a pce of about 7-9.

I agree with Callie that the test cylinder looks a little slumped and may have begun to bloat.  Cone 2-3 might be a good test for next time

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Unfortunately, I have not been able to edit my picture size-yet. Edit button does not come up when I double tap pic.

This piece is just slightly larger than a shot glass: 1/8lb. of clay perhaps. Spent perhaps 30 seconds forming it and then into the hot sun it went. All I know at this point is: WOPL = 29.  Nearly zero plasticity. All material passed through 100 mesh screen,  and less than half through a 200 mesh.  From that:  alumina 30%, silica  45%, iron 12%, potash  5-6%, titanium 3%. All guesses of course, but comparing the WOPL, color, and mesh sizes to my extensive clay database: close.  Will do more formal testing once I figure out if it produces the color and effects I want. Threw away a couple thousand test bars few months back, so pardon my refusal to make more at this point.

Nerd

Edit: I am wondering if this is a chlorite group/ clay.  2:1:1 with double tetrahydra inner layers: iron fe2 / fe3.  This is close enough to the Arkansas border, where chamosite deposits are common. If that holds true, then iron levels can be over 20%. 

Edited by glazenerd
Information added.

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Chlorite can definitely be a component of a red brick clay.  How much, I'm not sure.  Secondary clays are always a mishmash of whatever and can be variable.  Government pubs can be a good source.   "Clay and Shale resources of Ontario" is where I get my info on local clays.  I tried searching for Missouri publications to help get you on your way, but the only one I could find was from 1896--Missouri Geological Survey's Volume XI "Clay Deposits"  by Herbert Alan Wheeler (I think he's the author, but not sure).  Sadly its information is quite crude and the kinds of clay minerals aren't in it.  Maybe there's a  new edition out from at earliest the 1970s?

I would venture a guess that the iron content is closer to 8-9% at the very extreme.   Which is the max listed in the above book regarding brick clays.  Based on colour, 5-7% is my guess.  Beyond 10% I'm not sure it would be terribly workable, maybe even thixotropic?  If it is 20% it would be more useful as a pigment (or iron ore, if you go for that kind of thing).

I'm sorry to hear you won't be doing any more firing tests at present.  If you're willing, maybe test for brittleness destructively and then have a look at the cross-section for bubbles and signs of bloat.  Your microscope would be instructive here.  

My guess is that it would be a good cone 8-10 single fire glaze base with a little more flux and silica.  Maybe even a tenmoku-kaki.  

This kind of thing is what I love abouy ceramics, the joy of a new material to play with. :)

Edited by Tyler Miller
changed a verb and swapped a sentence

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Tyler: decided to mix an 04 frit ware body, using 25% brick pit clay.

25% high iron local brick pit clay

25% OM4

30% frit 3110

15% A75  silica

5% (IP) plasticizer.              And the result with low expansion clear glaze 1960F peak / 5 min hold 

good call Tyler.   Have a C3 and several C6 variations coming up shortly.

image.jpg.31e84552de4849cada59be6675fa62ce.jpg

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