What is this streak?

[wesles24]

Just milled fresh cut oak and this blue/purple streak appeared right after the cut was made. I am new to milling and wondered if anyone here knows what it is? Is the board still good? Also can someone tell me if this other tree is a sycamore and weather or not it is worth milling (30" wide)? I've heard it is hard to dry.

Thanks!

 

[bobbobbobbob]

Looks like tannins reacting with something you cut through. I wouldn't be worried.

Sent from my SM-G930F using Tapatalk

 

[BobL]

It looks like a bit of metal has been trapped in the tree.
Much of that stain will come out using a solution of oxalic or other organic acid.

 

[rarefish383]

Steel reacts blue, copper, lead other metals do not. It will be darker, closer to the object, and it is probably at fence , bird box, or clothes line height. Just for kicks call a local mill and tell them you have a beautiful straight, limb free Oak log, with these really cool blue marks in it, and see what they say, Joe.

 

[babybart]

Yes, the other tree is sycamore. Mill it, because it isn't good for anything else!