wens

Probably. 
Part of the fun of working with found materials is the variability. Sometimes close enough is all that’s needed.

I make terra sig regularly with my local clay and follow something similar to @Magnolia Mud Research’s post. I don’t go to great lengths to extract any remaining “finest particles” from the dregs. I played with that a bit but found it was counterproductive.  Letting it slake a few hours then mixing it really well gets the all good stuff in suspension. 
I’m sure this is derived from Vince Pitelka or maybe Pete Pinnell, but it’s what I go with:
1 quart water to 1 pound of clay. 2.5 grams deflocculant per pound of clay.
My deflocculant is half soda ash/half sodium silicate. 

Agreed, but with it so thinned out I couldn't get a true specific gravity to plug into the formula - it was too close to 1. Next batch, I'll try not to thin it out too much. Appreciate all the info!

I think you may be right. Where I live, it's all red clay, rocks, and tree roots, but I did try to dig some that was less organic. I've followed Vince's method for all my other sigs, but there are so many methods out there that are more "shake it up and let it settle and pour off." Maybe I should give up some control.
I don't know what color it will fire to, but here's a bone dry mini-bowl with Redart sig on the left (didn't stir it up very well), and ditch sig on the right. Hard to see the shine in the photo, but it does buff up nicely. I had some of it evaporating in a shallow pan with the dehumidifier on.