Does this occur naturally?

[Beamer1879]

Naturally or possibly man made?

 

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[dirtfishinMS]

I'm not an expert by any means, but just using my limited knowledge and deductive reasoning..

The mortar like pit CAN be produced naturally in a creek in the right circumstances. Usually (I imagine) a rock can get set into a shallow running part of a creek or river and a small pebble falls into a small fissure in the rock. The running water causes the pebble and future pebbles to move in a circular motion, slowly eroding a pit. I know that occurs.

However, the smoothing of ALL edges of your find confuses me. For yours to have occurred naturally, it would have had to have formed the pit first, then at some point the larger stone broke off somehow from a larger stone and then was creek worn over the many many many years.

Iono. Just an educated but uninformed opinion.

 

[Red-Coat]

Welcome to Tnet

It most certainly can occur naturally. There's a particular form known as an 'omarolluk' ('omar' for short), which occurs in greywacke cobbles that have been glacially transported from Hudson Bay in Canada and deposited widely across the Northern parts of the US. They're frequently claimed as (mistaken for) Native American cupstones.



The one above is pretty crisply defined, but of course they also erode and weather to give an appearance like yours. The tell-tale distinction between natural and man-made (or natural but man-used) comes from close examination for signs of use-wear within the cavity. Rarely seen, and the majority of such stones are purely natural.

Wiki entry here:
https://en.wikipedia.org/wiki/Omarolluk

The name has been extended (wrongly) to include similar rocks from other regions; although they have formed by essentially the same processes (erosion of carbonate concretions from their host rocks after they have broken open), they aren't omars as geologically defined.

 

[Beamer1879]

Thank you very helpful

 

[ToddsPoint]

I'd say there is a chance that it is an artifact because the depression is perfectly centered on the rock. These do occur naturally quite often though. Gary

 

[Beamer1879]

I thought this as well because it wasn't near a water source and it fit so perfect in my palm, it was like it was held before.