ArmentaOld World Midnight Boulder Opal Stack RingDetailsStackable Armenta ring from the Old World Collection. Midnight signature oxidized sterling silver. 18-karat yellow gold bezels and Cravelli stations. 0. 55 total opal carat weight. Made in the USA. Designer About Armenta: When Texan Emily Armenta first created a feminine, Spanish-inspired line of oxidized sterling silver pieces set with diamonds and gemstones, her goal was to create romantic jewelry with a rocker edge. Her Armenta collection of distinctive jewelry is a favorite of Hollywood's elite.