Silver Whitby Jet Marcasite Round Ring. R747. This petite, feminine Sterling Silver, Whitby Jet and Marcasite ring features a circular central piece of Whitby Jet that has been sourced directly from the north east coast of Yorkshire. The striking stone is surrounded by sparkling pieces of Marcasite and set on a classic silver band. All our Whitby Jet jewellery is designed and crafted within our very own workshops in Derbyshire where a team of skilled craftsmen turn the raw Jet into these stunning pieces of jewellery. You can find other matching Whitby Jet jewellery and other Whitby Jet rings on our website. Silver Whitby Jet Marcasite Round Ring. Whitby Jet 3mm diameter, top of ring including Marcasite 9mm diameter.