>>Long Meg's rings have a dark smooth look which I assume is finger oil from people tracing the patterns.

Nice to think of the many generations of people who must have done that...

The carved area of a stone is usually kept cleaner than other bits of the stone, swept of debris etc... so much so that sometimes I think it's strange when there's lichen there....

When we were at Little Meg on Sunday I'm sure I could see the lichen inside the grooves had been flattened almost as if someone had applied pressure to it, perhaps with chalk perhaps with fingers.