STAY AWARE OF THIS.
Before starting I recommend to transfer your bitcoins to another wallet!!
They are asking you to export your private key to their site in order to be able to claim those bitcoin diamonds.
This is a very shady practice, and maybe those guys are never going to scam you, but why if there is a script or just a counterparty thaet can easily collet your data and then stole your funds?
Be careful people, do not risk all your money just for a single bucks, they can easily be earned with hard work, nothing more.