Need help with rock id please.

[seahorse]

Found about 6 inch under sand against tree with a few holes around and a couple of sunken places a few yards out from tree.

 

[DDancer]

Aside from where you found it anything you can tell us about it that peeked your curiosity?

 

[seahorse]

Yes and thank you much for your reply. There are some signs and symbols close by . There is a large rock about 8 feet down from where i found this rock that i could only touch with 3 inch pvc pipe with water hose attached to top of pipe to help sink it down in sand. My question is could this be the same type of rock at 8 feet and should i dig. I have seen no other types of rocks like this around area.