The Stone of Earth is granted to those who purchased the Knight of the Feywild Pack and is sent to the character in a [Knight of the Feywild Supplies] box following completion of the quest Sleeping Dragon Bridge or after a moment after logging in for characters that have completed it already. If lost it can be replaced via the Reward Claims Agent in Protector's Enclave either directly or in another instance of the above supply box.
The Stone of Earth consists of a choker collar with a small leaf decoration. When first equipped the Stone of Earth generates a chunk of earth floating just in front of the wearer's neck, as well as an occasional green glow from the area of the leaf: Both effects will occur even if neck slot visuals are disabled and / or the character's appearance is in Fashion mode. After a short time the earth chunk will vanish but the glow will remain. This may or not be intended behavior/positioning based on prior descriptions. If the Stone of Earth is used as an image source for the "Change Appearance" function only the look of the necklace applies: The glow and earth chunk traits are linked to the true item only.
NOTE: This is a NECK item even though the in game tooltip currently reads ring.