Green Jade "Longevity" Symbol Pendant Necklace on Leather Cord, 18" Gemstones may have been treated to improve their appearance or durability and may require special care. The natural properties and composition of mined gemstones define the unique beauty of each piece. The image may show slight differences to the actual stone in color and texture Jade is commonly treated and impregnated with polymers to enhance its color and improve its stability.