attention geologists, page-2

Arkose - pronounced Ahh-Koze.

It is a form of sandstone, which is to say it is grains of feldspar and quartz (mostly) cemented together either by a calcareous (limestone like) cement or a clay rich cement.
Cement in this case is a geological term, and does not refer to the stuff your house is built with.

Last time I checked, Xenotime (Zen-Oh-Teem) was NOT a feldspar. It is a phosphate of Yttrium (pronounced Ittree-yum). Xenotime is an accessory mineral (meaning does not constitute a majority mineral in a rocks makeup) that either grows in pegmatites (which are "veins" of all the funky stuff that doesn't form normal rock forming minerals easily) or grows as a very thin rind around zircon in sandstones (like arkose) and other rocks made up of sediments. Often, xenotime will have the Yttrium replaced in minute quantities by other elements such as uranium, thorium, and some of the Rare Earth Elements (REE's).

For economic extraction, it will be pegmatitic xenotime that is the target. Please don't become confused between the two settings for xenotime growth. Pegmatites can be injected into any sort of host rock.

Pegmatites are great rocks - they are made of of the water rich leftovers after all the other stuff has cooled and crystallised out of a magma to form rocks - imagine the whey left over after the curd has dropped out to form cheese. All that is left is the stuff that doesn't slot into crystal lattices easily and so doesn't readily precipitate out in common rock forming minerals. Fortunately, a lot of these funky "incompatible" (proper term) elements are useful materials, like Uranium, the Rare Earths, Tantalum, Lithium, Boron and so on and so forth which end up concentrated in the pegmatite.