Oval Mother of Pearl with Marcasite Accents Ring .925 Sterling Silver Ring. Substantial and comfortable piece that makes a statement. 18 x 14mm Oval Shape Paved with Sparkling Marcasite around Oval Mother of Pearl. Floral Marcasite designs on Ring Shoulders providing more visual interest. Stamped 925. 13 x 10mm Oval Simulated Coral Stone. High quality Marcasite.