AAA Grade Swiss Blue Topaz pendant necklace. These Swiss Blue Topaz gemstones measure 5mm and have been set in a sterling silver, with a hint of rhodium, prong setting. Swiss Blue Topaz is known for its electric sky blue coloring. The Italian sterling silver 18" box chain has a rhodium finish. Why you ask...this touch of rhodium slows down the tarnishing process, that's less polishing for you. Beautiful delicate gift choice for the minimalist in your life.