In vampire diaries, what is anna's necklace? Where did she get it from?

I ask this because I'm curious, that black necklace that she wore was
very suspicious. And no matter where I looked for the info for it, I
couldn't find anything about it. Ask.com, Google.com,
vampirediaries.com.. you think it, I tried it. I'm writing a
fanfiction and I'm trying to figure it out. I suspect it was from
Emily or whatever but that still doesn't do much for me. Help?