I don't how your stuff is, but the chert here in the KS  flinthills is a bluish gray when I dig it out.  But if I pick it up off the hillside it is a tan to brown color.  I don't know if thats from thousands of years in the sun or prairie fires, but if its Brown it really works nice.  I been meaning to ask you iowabow, over there along 34 before you cross the bridge to Illinois  there is a rock cut along the road with some white seems  in the strata.  Is that good chert  or is it chalk?  Josh