Men's 0.925 Sterling Silver Simulated Opal 1.5" Irish Celtic Knot Cross Pendant 1mm Rope Necklace, 20" Type: Celtic Cross Size: 39mm x 20mm Finish: Antique Metal: Sterling Silver Purity: 0.925 Birthstone: Simulated Opal Back Side: Solid Jan: Garnet Feb: Amethyst Mar: Aquamarine Apr: (Simulated) Diamond, CZ May: (Simulated) Emerald Jun: (Simulated) Alexandrite, Pearl Jul: (Simulated) Ruby Aug: Peridot Sep: (Simulated) Sapphire Oct: (Simulated) Opal, Tourmaline Nov: Citrine Dec: (Simulated) Tanzanite, Turquoise, Zircon <span class="a-text-bold">Genuine: </span>Are mined from the earth and are created by nature. <span class="a-text-bold">Synthetic:</span> Are grown in the lab and will share all the characteristics of the nature gemstone. They are identical in chemical composition and optics to the real gem. <span class="a-text-bold">Simulated:</span> Are imitations of a real gemstone in looks only, but shares no chemical or optical characteristics. It can be any material that looks like a real gem.