Silvery Black Pearls

by Madeleine
(dorset England )

Hi
I was bought some pearls couple of years ago by a friend from a jewellers in London but have no idea what type they are. I have attached a photo for you to see. They are a blue grey colour and approximately 7mm in diameter. Sorry for my ignorance but I'm sure you know far more than I do and it would be great to learn what they are as they're so pretty. Thanks for any help you can give me.