Eldarium Locked Chests in Elder Vaults

How do you unlock them. People have said skeleton keys but this is just not the case. I have 20 on me and keep getting the "you need a key" message. Tried a few vaults, no luck. Anything good in these chests?

EDIT:In case you're having the same difficulty; I was just clicking on the chest. You must click directly on the circle at the top center of the chest. Totally my bad. Containing legendary items.