size: 17 x 9 mm weight: 1.53 grams material: 18k yellow gold gemstones: natural mexican water opal: 2.93ct necklace not included. only meant for display. Notes from the Curator This oval cabochon-cut pendant holds a Mexican water opal, the colorless-to-near-colorless variety distinguished by its bluish or golden internal sheen rather than a solid body color. Water opals lack body color and appear transparent, yet exhibit play-of-color—an iridescent shimmer of rainbow hues that move across the surface as the stone tilts in light. Mined primarily in Jalisco, Querétaro, and Hidalgo, this opal variety has been cherished by indigenous cultures in Mexico for centuries. Mexican opals form through the interaction of water with silica-rich volcanic rocks found in extinct volcanoes, and are composed of hydrated silica containing between 2 and 10 percent water by weight. Completely transparent colorless-to-near-colorless opal usually achieves a premium, prized for the depth and brilliance of color flashing within a crystalline window. The prong setting allows light to enter from below, intensifying the opal's spectral dance.