In Norse Mythology, The Yggdrasil is an evergreen Ash tree that spreads over the 9 worlds of the Norse Kingdom. It is a highly sacred place, where the gods will assemble. It is seen as a symbol of protection in Icelandic culture.
These pendants have a 3.5cm diameter and are quite new at my store here in Iceland, though the Yggdrasil jewellery is among the most popular amongst native Icelanders.
The back of this necklace is hollow, as depicted from the front.