(Gem OC) Boulangerite

 Boulangerite aka Boulang (Member of White Diamond's Court)
Gem Location: Scalp (The gray streak of hair)
Weapon: Needles 

Boulangerite is actually more of a mineral than a gemstone. She can pull out strands of her gem to summon her weapon(s). Her personality is of a typical Yandere who likes sharp objects and loves to stab people/ things with said sharp objects.

, this was the gem I was talking about. You can use her as an antagonist in your story. I hope she's to your liking.