J6120-18-AB Sterling Silver Swarovski Crystal Oval Pendant in Gift box Size = chain approximately 18’’ crystal Drop 18mm. Swarovski STRASS® crystal is characterized by razor-sharp cutting of facets, prismatic brilliance and lead content in excess of 30 percent. An invisible coating on the crystal makes it easier to clean. Aurora Borealis first made its sparkling introduction in the mid fifties, after Swarovski made important advances in crystal production. By experimenting with the manufacturing processes by coating crystals with extremely thin layers of metal and vaporising in a vacuum, they were able to increase the sparkling power of the crystal. Named after the spectacular play of the northern lights, this innovation has become a success worldwide and started a fashion trend of coating stones in a variety of colours with shimmering effects. AB as this effect is often referred to, continues to fascinate and cast a magical spell on crystal enthusiasts. Glistening in all colours of the rainbow, this special effect has established itself with crystal buyers the world over.utting and polishing are done by machine to achieve optical clarity.