Any geologists in the house?

[Neil]

I came across this cracked open boulder while ascending a brook in the Macintyre Range.
Any thoughts as to what sort of rock this is and what cooling history would result in it?

http://adkhighpeaks.com/neil/outdoor pursuits/avy-macs_2016/Avy-mac_0044.html

 

[TJsName]

Maybe this? Not sure.

https://en.wikipedia.org/wiki/Labradorite

 

[Neil]

On MYCCR someone posted this link in response to my query there.

 

[TJsName]

Could be a coincidence.

 

[Raven]

Labradorite has a distinct way it interacts with light; it looks like its referred to as labradorescence in these links. Moving it back and forth in the light, light enters and is reflected/refracted back giving a variety of colors. It's a pretty unique stone. I have a piece about the size of a baseball on my table, primarily green and blue. I'm no geologist, but it could be the same.

Did you notice any unique play with light?

 

[Fitz]

The mineral is likely labradorite. The rock is likely anorthosite.

https://en.wikipedia.org/wiki/Anorthosite