Another one that makes you go, "hmmmm?"

[firehorse12]

Iron? Rock? Bone? Hmmmm.

 

[bountyhuntergirl86]

Where do they form

 

[Archeodeb]

I learned something new once again, I am liking this answer, here are some photos of petrified turtle shells https://www.google.com/search?hl=en...09.254.3j1.4.0...0.0...1c.1.4.img.DtOBDoYFLfo

These are most definitely NOT petrified turtle shells. Just from curiosity, I went to the link above to look. With one possible exception, nothing in that image search shows a petrified turtle shell. I think you may be using the term petrified when you actually mean something else entirely. Most of the examples that were not merely rocks, and rock carvings, were casts or molds (most not even related to turtles). Casts are formed when sediment fills a vacated cavity in the soil or mud (vacated because the thing -- in this case a turtle -- simply rotted away and left a void). The cavity, itself is the mold or negative impression, while the cast is a positive reproduction of the exterior of the original. Those are not the same thing as petrification -- which would involve an actual turtle shell becoming completely mineralized over a very long period of time.