Nature Done Wright

On Monday, in advance of my High Mountain talk for Fyke and a field trip to HM's Franklin Clove, I wrote:

Thought I'd throw stones out there to see if anyone knew what they are. 

Found this on High Mountain earlier this year. What is it?  (Not sure myself.)

Ginny Chucka posited: "My brother Doug thinks it's Metamorphosed Granite Hornblende or Gneiss … " Marianne Herrmann wrote: "I think white granite can have grey streaks like that…."

I, too, took it for granite. (World's oldest rock joke.)  Gneiss! (World's second-oldest rock joke.)

Thanks, Ginny and Marianne.