I collected this rock during the summer of 2008 in the Pindos fold and thrust belt of the Peloponessos near the village of Ano Karyes. I like this rock because it keeps me quite humble as I try to think about all the factors and conditions that created such a fractured ‘mess’ of this rock. And I puzzle over how it holds together without just falling apart in my hand.
The chert is quite stiff, i.e., it has a very high Young’s Modulus of elasticity. During elastic deformation, a significant amount of stress can be introduced into this rock without creating much in the way of elastic deformation. Strain energy builds, and then is released upon the formation of a fracture. To release all of the strain energy, this kind of rock must be fractured in a very close spaced manner.
Age & Formation
Radiolarian chert from within Chert Series Beds of Jurassic age, ~180 Ma., Peloponessus, Greece.