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Spherical concretions > photos


The spherical concretions from Feleac are sedimentary rock materials that were cemented together to form a hard structure. The surrounding sediments slowly erode away, exposing the concretion. They were formed when calcium carbonate and other cementing minerals precipitated from the ground water around an organic nucleus, like a shell. Near Feleac we can find sphere-, and cannonball-shaped concretions. In the past they were often used as construction material.

Comment by Len Hudgens, a geologist: Concretions, or boulders as we call the large ones are common in the elephant rocks area. Ones in the glaciated areas are called "erratics" because they were moved and rounded by the glaciers. However, certain rock formations also erode to form concretions or boulders if there are minerals in the rock that is slightly harder than the surrounding matrix. Iron oxides in sandstone, as in the "Garden of the Gods" area of southern Illinois, is a good example.
Cracked man-sized concretion  
   
Man-sized concretion
Roots  
   
Roots
Cracked concretion  
   
Cracked concretion
Concretions grown together  
   
Grown together
Cracked concretion  
   
Cracked concretion
Spherical concretion  
   
Spherical concretion
Sphere in the concretion  
   
Sphere in the concretion
Sphere-shaped concretion  
   
Sphere-shaped concretion
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