In order to begin this quest, you must first have the Hunter's Lost Charm on you. This will give you this dialogue option when speaking to the huntsman:
Give the charm.
What is this? Oh my. This... this charm belonged to a dear friend of mine by the name of Adamar. He left a while ago on some dead end quest in search of this, Jewel of Eranath, if it even exists. I tried to convince him not to go on this wild goose chase but he would not listen. You finding this charm gives me great concern over his safety.
Perhaps you could look into this matter for me? I don't really know where you could start, but Adamar did leave behind a few things. He had some research notes and this strange piece of mineral that I had never heard of. In his notes I believe he mentioned something about a key and a Sea Scholar or something along those lines.
I don't know, perhaps you could start there?
He will give you the book "Adamar Research Notes" and the Calamite Ore. Although the journal entry directs you to craft a moonrock key, it is not required yet. To finish this quest and continue the quest chain, you simply need to go speak to a Sea Scholar and you will have the dialogue option 'Ask about Adamar'.
Ask about Adamar
Yes, what can I do for you? Oh... you say you are looking for someone named Adamar? Hm... Adamar... Adamar... the name sounds familiar.
Oh yes! I remember a man that went by that name. He came by here recently in search of some information regarding a cursed chest. While we do have information in regards to such an item, we can't just give it out for free. I told Adamar that if he wanted the information, he needed to retrieve an item for us. Unfortunately, he hasn't returned. Perhaps you'd like to pick up where he left off?