Question About Harpy Mountains

[temps]

There's this rock in the mountains near the harpies in chapter 2 when you're doing the witcher's contract on harpies for the guy in the nearby hut.. Geralt keeps saying something like "my medallion... magical danger" when I'm near this boulder in the mountain valley... but when i use the medallion it seems to "highlight" this boulder nearby in red. I approach it, and nothing happens. Am I supposed to do something here?

[Rudi-v]

Those rocks are related to a quest that you get when you 'read' the dream crystals in the harpy lair.