IMO, they are a part of a "gift" which you get sometimes. You can get similar gifts in other locations, too. But I don't know (and I would like to know!) when and where you get the gift exactly.The gift is a rain of better stuff when you enter the area. In Harmondale you get Moonstones, Mercury and Elven Bows, in Erathia you get 2 lamps and about 5 additional pieces of Erudine ore. And so on. AFAIK, the gift in Erathia is related neither to your Perception not to the direction you came to Erathia for the first time.
A simple check in Erathia: Take the direction to Deyja and search a lamp near the highest point of the trail. Either you find a lamp quickly (continue searching another lamp and Erudine ore) or you are out of luck.