Mystery mineral from road base.

[LanceH]

I didn't want to ask here but I've scoured the mineralogy sites and can't find any match and the Mineral groups on FB won't let me join. 

I have this large rock I pulled from RR track base.  All the base was the same meterial.

 

Any clue to what the mineral is?  It's fairly brittle.

 

 

[DPS Ammonite]

Probably potassium feldspar. 

Will a piece of quartz and a steel knife blade scratch them?

 

Try Mindat for another opinion.

[LanceH]

Well, I can break it with my fingers.

The feldspar examples I see in pics are certainly the closest match so far.

 

THANKS!

Edited February 26, 2023 by LanceH

[Tidgy's Dad]

Yes, I would have said it's something close to orthoclase as well. 

Nice.