Silver Blue John Domed Oval Ring. R719. This stunning statement ring boasts a striking domed oval shaped cabochon of rare Blue John stone that has been sourced directly from Treak Cliff Cavern in Castleton. The stone is set within contemporary sterling silver and completed by a classic silver band. All our Blue John jewellery is designed and crafted within our very own workshops in Ashbourne, Derbyshire where a team of skilled craftsmen turn the raw Blue John stone into these stunning pieces of jewellery. You can find other matching Blue John jewellery and other Blue John rings on our website. Silver Blue John Domed Oval Ring. Blue John stone 21x8mm.