12mm = .47in (Most Popular Size) See last pic for size comparisons. A beautiful clear colored stone that sparkles with aurora borealis, making it truly earn its name....it’s just magical! Nickel & Lead free zinc alloy, perfect for sensitive ears. made in a Texas boutique. Aurora Borealis, commonly known as AB, is an effect which was jointly developed by Swarovski and Christian Dior in the 1950s. AB — a shimmering opal-like finish that truly enhances the beauty and sparkle of cut crystal.