Silver Turquoise Marcasite Shield Ring. R819. This feminine Sterling Silver, Turquoise and Marcasite ring features a circular central piece of Turquoise, the December birthstone. The striking stone is surrounded by sparkling pieces of Marcasite set into a sterling silver shield and embellishing a classic silver band. All our Turquoise jewellery is designed and crafted within our very own workshops in Ashbourne, Derbyshire where a team of skilled craftsmen turn the raw Turquoise stone into these stunning pieces of jewellery. You can find other matching Turquoise jewellery and other Turquoise rings online and instore. Silver Turquoise Marcasite Shield Ring. Turquoise 7mm diameter, top of ring 25mm diameter.