Sterling Silver Gemstone Heart Curb Chain Pendant Necklace, 18" Sterling Silver necklace featuring heart shaped natural Jade & Crystal Accent. Sterling Silver 18" Curb Chain. Spring Ring Clasp. Jade is commonly treated and impregnated with polymers to enhance its color and improve its stability. Marcasite can appear iridescent in the light. 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.