Ironstone Concretion, South Wall.

On Sunday night, 16 Sept., I bought and
downloaded from the AJS Richard Nickelsen's article
"Sequence of Structural Stages of the Allegheny
Orogeny at the Bear Valley Strip Mine, Shamokin,
PA," Volume 279, March 1979, American Journal
of Science.

http://www.ajsonline.org/

Much to my surprise, I found a photo of this
concretion in Plate 2 on page 231.

Photo Copyright Dave Kerr, 2007.