Not a great deal, unless you have a large & perfectly shaped/flawless crystal & can prove its provenance. Even then, you might get a decent sum but don't plan to retire on it.
In the past, a big annoyance in the hills were the "collectors" who thought nothing of lugging a cold-chisel & sledgehammer with them to pulverise any likely looking rocks, repeatedly. Instead of using the traditional method of scouring the debris in run-offs or the aftermath of rockfalls after the spring thaw. Nothing other than sheer vandalism IMO!
IIRC, Most of the Cairngorms on sale today don't come from Scotland, instead they are imported in bulk from South America.