A quarry just north of Keswick, Iowa had exposed the white chert nodules and some of the nodules contain white agates sometimes laced thin red to orange bands. The agates with red bands from Keswick may be the most desired type of agate coming from Iowa and Iowan collectors would pay premium prices for good specimens. Since the quarry is privately owned, it's quite difficult to obtain any agates from the quarry despite the fact that some people sometimes sneaked in to obtain some.  Many specimens are fractured by mechanical quarrying that they're best left in their natural forms without any cutting or polishing. Recently, few club field trips were made to the quarry, and I have yet to hear of anyone finding the classic agates from that location.