Blue Tanzanite Earrings 4 mm Round Cut in a Buttercup Sterling Silver Stud Earring Setting A pair of natural blue tanzanites in buttercup settings which makes them look a bit wider. Each pair comes in a small cotton lined gift box. This is made with 925 hypoallergenic sterling silver for your comfort. Blue Tanzanite Earrings 4mm Round Cut in A Buttercup Sterling Silver Stud Earring Setting