What caused this pattern of weathering?

[mcl]

Got a rock I found in a pile of landscaping rocks. It looked interesting so I picked it up to consult the experts. What type of weathering causes this?







Sorry, my wife's new puppy desperately wanted to help take these pictures..

 

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[Slingshot]

I've been looking at rocks most of my life and never seen anything like that. Better pics for close up would help, but my first impression is of an Indian playing around with a drill and a bit consisting of a reed with sand being used as an abrasive to get that effect on the stone.

 

[mcl]

I did my best, but my camera is only so good. I took these by taking pictures through a magnifying glass.





I'll go see if I can find any others. Maybe they'll be easier to see.

 

[mcl]

Well I went back out and surprise surprise, I couldn't find any rocks exactly like that one (I mean, it is a rock after all). A lot of them had pitting, but most just looked like holes whereas the ones on the rock I posted had a bit of a ring shape to them. I did find one other rock that has something that COULD be a large version of one of those pits, but please forgive me when I say that I don't know my head from my.. rock.. when it comes to rocks.

Here is a picture:



There's just one of thing thing I'm talking about. It's centered more or less in the image. A ring of ridges (like on a Bingo chip) around a slightly raised center with about seven dots on it. Honestly this could be something completely different than the first picture, I have no idea.

That same rock had some other junk in it too. At least a few spots with ridges, couple angles here show 'em.





And a cheeky little pattern of weathering that looks like a bird walked in wet cement.



This is all probably irrelevant but I like show and tell time?

 

[EricTheCat]

To me this resembles fossilized coral or something similar. I have seen similar pieces around here. It could have been tumbled in a river making it rounded with weaker details wearing quicker/breaking away leaving the pattern. Cool piece.

My cat often does the same thing as the puppy in the last pic when I am trying to photograph things.

 

[EricTheCat]

2nd rock definitely looks like it has part of a brachiopod fossil in it (and looks like probably quite a few other fossils in it too).