A friend recently made a Facebook post on getting caught in a patch of quicksand while hiking and camping in the SW US. I posted back about getting caught in "hex mud" in the Au Sable River in Michigan. Another friend asked if hex mud is real, since she couldn't find it in Google. I sent her a brief description. Now I'm in danger of hex mud being viewed as a fish story. Google and Bing have failed, at least in the first several pages of responses, to provide corroboration. Does anyone know of an available source in print which describes or at least mentions hex mud?

Thanks,
Ed