Re: I think my bees are attracted to minerals in a freshly exposed ledge area
I compost virtually all of the waste paper that I accumulate, but I often let it sit in a bucket of water for a few days to soften up before the paper goes in the compost bin.
For the last 2 weeks bees have constantly been working the wet paper standing above the water in the bucket. There are plenty of other water sources available, but they persist in coming to this wet paper bucket.
I have concluded that they may be harvesting fibers from the wet paper to mix/make propolis. It may be that your bees are after the moss for similar purposes.
-- Victor Hugo -- "Common sense is in spite of, not the result of, education.”