Rock with weird formation on it

[cloudboy]

Found in West/Central KY, in a stream.

 

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[Red-Coat]

Very neat. I think that’s a secondary sedimentary structure formed by mineral precipitation in a fracture. Some people call them ‘Liesegang’ bands but, strictly speaking, this refers only to structures with a concentric ring-like appearance although they all form in a similar way. They’re relatively common features in sedimentary rocks, especially sandstone which is rich in iron oxides. Chemical weathering and differences in resistance between the mineralised bands results in this kind of relief pattern which can occur in large expanses with a repeating geometric pattern. When found in large exposures, it’s sometimes called ‘carpet rock’.

Here’s an example of Liesagangs in sandstone where the ring structures are constrained by those in linear fractures. You won’t always find both types together.


[pic from Richard Childs’ ‘onlandscape.co.uk’]

 

[bravowhiskey]

x may mark the spot. lol. Cool looking Geofact cloudboy