Trustmark 925 Sterling Silver 6mm Deep Sea Coral Created Opal Ball Stud Post Earrings, Cala Add the beauty of Deep Sea Coral to your wardrobe with our Cala line of created Opal ball stud earrings Features our stylish 6mm bead or ball size which measures about 1/5 of an inch. Made with solid 925 Sterling Silver. Professionally hand-set in our own US studio.