Help! What Is This Crazy Looking Green Rock With White Spots?

[Theodocious]

At the beach, and saw this rock in the sand. It is quite heavy, solid and surprisingly smooth. I have no idea what it is. What is it?






Thanks for any inputs!

 

[ToddsPoint]

Looks like some type of porphyry. Indians used that stuff to make celts and other artifacts. Gary

 

[Theodocious]

I looked online, and the closest thing was a photo of a similar rock that was labeled 'Alaska river rock.' But there were similar images of porphyry stones as well, and I wanted to make sure. Thank you for the information!