78.59Ct Ammolite78. 59ct Ammolite hand cut and polished. Set in . 925 Silver. Necklace is 20" Center stone is approximately 1. 25" x 1. 50" Ammolite is a rare, opal like gemstone composed of the shells of fossil ammonites. It is highly iridescent, frequently exhibiting red, green, and orange colors that flash differently depending on the angle of the light. More rarely, ammolite will also flash brilliant blue and purple hues.