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.
i posted a few microscope pictures up top. what i neglected to mention is that the stretched crystals recrystalize, so single crystals won't lock stretched under the microscope. but you can (maybe) see the white crystals, which is quartz, then some brownish stuff, which is either impure quartz or mica crystals, and some black platey stuff, which may be biotite mica
but please: see disclaimer in above post. i could be talking out of my ass
Disclaimer: So, I am very interested in this topic but i am no petrologist or anything. So take everything I say with heaps of salt.
But:
From what I understand though it's different materials. Gneiss is highly metamorphosed, meaning subjected to high heat and/or high pressures. So the source rock (often granite) is squeezed and stretched and the discrete crystals stretch into this layers. It's also pretty easy to see under any optical magnification, that there are different types of crystals and minerals in the different bands. At least to the untrained eye it looks like it.
i mean maybe some distros will add something, i don't know. and i don't care because i don't have to. shit like that is deinstalled faster than an llm can print an emdash.
there is not much in my life that i loved and hated with this much passion at the same time. i love what you doing and hate you for it. please keep doing what you do, you beautiful human
oh cool! Flint nodule?