This is an example of a rock formation known as “septarian concretion”. The polished specimen in this online jigsaw puzzle is located at the Museum of Nature in Ottawa, Canada.
Jigsaw puzzle subject image credit: Special thanks to subarcticmike for making the photograph used for this jigsaw puzzle available through the Creative Commons Attribution license. Visit subarcticmike's Flickr photostream.
See all jigsaw puzzles based on subarcticmike's photographs.
Category: Other Nature