Found within the chert concretions, the agates of Coldwater Quarry at Vinton are white to gray and there are no reported cases of Coldwater agates having any colors. It appears that they share the same limestone formation as those of Union Road agates from south of St. Louis, Missouri. It was said that they were available only for a short time during the quarrying of limestone before it was closed few years later.  Apparently, the term "Coldwater" was used for white agates found in different places in Wisconsin, Illinois and Missouri but I would not recommend applying that name to other white agates from different locations so to avoid any confusion.
Rough Appearance: Yellowish-tan chert concretions sometimes with white agate showing.
Can be confused with Union Road Agates and except that Union Road Agates are always more colorful.