Can someone help identify this rock?

[TheMaineAgenda]

Hello,
My son found this rock about 15 years ago and I have always kept it because it is so unique. I have no clue what it is. It was found in Maine. Does anyone have any ideas??

Thanks all !

 

[Red James Cash]

Glass slag i believe.

 

[unclemac]

although it has the color of boulder opal, i have to go with slag glass too. pretty thing however...

 

[Red James Cash]

pretty thing however...

Yeah it is isnt it.