Thank you for all of the wonderfully creative naming suggestions! The one that stuck slipped in quietly, but it gradually seemed more and more perfect. And although the mitts aren't exactly the shape of a cairn, they'd be great to keep your hands warm while carefully placing stones, and many cairns either start off as rings of stones or disperse until that's all that remains.
The only photo that I've taken of a cairn that I could find was this, taken from inside a rather ramshackle one.
Those who have ordered the Whimsical collection should have already received it, but if you're interested in purchasing this one individually you can find it here.
p.s. Ishbel already resulted in me adding a new category of pattern to my shop, and since I didn't have any other mitt patterns and I can only put a pattern in one category I listed this under hats - which is really rather imperfect. So, since you're the ones using my navigation, how do you think I should categorise my growing pattern collection. Replace hats with accessories, even though they'll be mostly hats? Get rid of the current system and create more categories, so that patterns can be listed under all of the appropriate ones? Do you care at all, or do you find yourself clicking through to individual pattern pages from blog posts, ravelry etc?