England or France 13th century. See Medieval Jewelry, Campbell, #22 for a similar example in the Victoria and Albert Museum, described as 1250-1300, England or France. That ring mounts a polished sapphire cabochon. This example mounts an 11.0mm polished rock crystal cabochon. Rock crystal, known as quartz in its colorless form, is found in a variety of colors including citrine, rose quartz, amethyst and others. This stone is pale green and clearly shows cleavage characteristic of rock crystal. The surface is lightly pitted from burial and with a natural cleavage pit to the top. The band is plain 1.2mm round section and the whole is plated in 24karat gold.