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[James Catmur]

This river worn rock came from a clearance sale in a house. The owners were Scottish and their children said this was a 'Cairngorm' but that could mean anything. The 6 sides, cleavage, hardness and density confirm that it is quartz but I have no idea where it is from. Clearly someone painted the exterior so as to make the interior look better. It is very transparent (if it were not for the black paint you would be able to see right through it).

Any thoughts welcome.

[SteveB]

Cairngorm can't mean anything. It means smoky quartz. Quartz is far too common for anybody to say where this poor specimen might have come from. You could remove the paint and clean it up and i doubt it would help its so unremarkable and out of context of its habitat for anyone to hazard a guess. Unless the paint is hiding a particularly distinctive matrix which nails the location.

[James Catmur]

The Cairngorms is a mountain range, famous for its smoky quartz and Topaz.

https://britishmineralogy.com/wordpress/?page_id=115

So, in theory, A Cairngorm comes from that mountain range - but as you say it now tends to mean smoky quartz. In the end I expect to label it 'Quartz' but thought I would see what others think. No matrix, water-worn, could be from anywhere

[Bob Morgan]

In 2014 Roy Starkey lectured at the Rochester Symposium on the Cairngorms, If anyone could help with this he could. I vaguely remember him noting differences between quartzes of at least two localities.