edit1: Some more photos of this selfsame rock through a micro scope (somewhere between 10x and 45x, didn’t write it down)

and another feature I discovered: the rock has a slickenside which i can’t really show on a photo. basically one of the sides is beat up into sand and polished. the whole rock unit was pretty beat up, so i’m not super suprised but it’s cool

edit2: ok i tried to capture the slickenside

  • SreudianFlip@sh.itjust.worksEnglish
    3·
    4 months ago

    Yep. Quoting my geomorphologist family member here:

    Nice but not gneiss.  Gneiss is in the mud rock continuum which has shale, slate, phylite and gneiss.  This is a banded lithic sandstone.  There is partial melting of the quartz forming some of the banding, but there is also original depositional gradation which is also responsible for the apparent banding.  The top has a component of limestone.

        • Masterkraft0r@discuss.tchncs.deOPEnglish
          2·
          4 months ago

          the more i think of it the more i doubt the sandstone again. i found this in a bigger region of high grade metamorphic rocks (mostly amphibolite, granulite). the specific place is a quarry where they quarry serpentinite as gravel. the rock unit is extremely busted up and crumbles basically on light touch into fist and smaller sized chunks. this rock, whatever it is, formed in cracks between the serpentinite. also for a straight forward sandstone this has a lot of mica in it and there are bands of nearly pure mica. i need to see if i can make take a picture with the microscope tomorrow.