Very heavy rock with strange holes - what is it?

Tsanden1 · Oct 7, 2017

I have been trying to find out what this is. It is from Arizona. Does anyone know?

vpnavy · Oct 8, 2017

1st - I noticed this was your very first post - so, Welcome Aboard! Take a look at Sub-Forums: Arizona for information (i.e., clubs, etc.) directly related to your state.

2nd - I moved this thread from Today's Finds! over to Forum: Geological Forums › Rocks/Gems for more exposure.

Golden_Crab · Oct 13, 2017

Looks like it was purposed by native americans at one point whatever it is..

diverrick · Oct 13, 2017

I found one similar in the Nevada Desert earlier this year no idea what it is, but I suspect it might be old coral, as we found other petrified coral in the area.

bloovey · Oct 13, 2017

to me looks like limestone and the holes are shaped by the waves of water.

smokeythecat · Oct 13, 2017

Welcome, the limestone sounds correct.

Tsanden1 · Oct 14, 2017

Thanks for the replies. It's quite heavy. I find it interesting that the erosion on one side of the rock has a similar but smaller pattern than the other.

dawnhvr · Nov 4, 2017

I have found many similar to that on Bethany beach in Deleware. Tiny crystals inside.

Goldfinger450 · Nov 4, 2017

Possible use in cracking acorns?? Welcome to the forum in any case. Got Ironwood Burl??

IAMZIM · Nov 6, 2017

I agree with Smokeythecat on this one.

Tsanden1 · Nov 16, 2017

So, I think I've cracked the case...
I was going on the assumption that because this was found in AZ, that it must have originated here. Apparently this strange rock has done some traveling. It seems the holes covering this limestone rock are caused by small mollusks called Piddock. They attatch themselves to the rock and the friction from their shells wears away at the rock when they move in a circular motion casing the round(ish) pitting.
Not sure how it made its way to this landlocked state...but there we have it. I think I should probably rehome this to someone with an aquarium.

EricTheCat · Nov 17, 2017

Tsanden1 said:
So, I think I've cracked the case...
I was going on the assumption that because this was found in AZ, that it must have originated here. Apparently this strange rock has done some traveling. It seems the holes covering this limestone rock are caused by small mollusks called Piddock. They attatch themselves to the rock and the friction from their shells wears away at the rock when they move in a circular motion casing the round(ish) pitting.
Not sure how it made its way to this landlocked state...but there we have it. I think I should probably rehome this to someone with an aquarium.

Interesting. I don't know about the geology in the area you found this in AZ, I find sea fossils around my yard in MN that are left from a shallow ocean that once covered the land here hundreds of millions of years ago. Just because the area you were in is dry now it might not have always been dry. Just something to keep in mind.