Luckily, I didn't buy it to wear. And I can confirm it's not a "cool rock".

Actual radioactivity matters quite a bit as to how safe it is, and that’s dependent quite a bit on the actual amount and thorium density of the specific item in question. From Tokaimura to a banana levels of radiation covers quite a large range, and I in good faith assumed that if someone was going out of their way to find and mention thorium on Unix socks of all places it was probably a pretty safe assumption that they know the basics and could check where on that spectrum the item falls, that it’s an excuse to play with a detector is most of the fun after all.