18ct Yellow Gold Whitby Jet Large Cushion Signet Ring. R180. This classic signet-style ring features a hand carved curved square Whitby Jet gemstone, which is inlaid into a thick band of 18ct yellow gold. Because the Whitby Jet is inlaid within the metal, this creates a beautiful smooth finish and creates a brilliant shine. Dimensions: Whitby Jet; 13mm x 11mm. Width of Band; 4mm. All articles Purchased from C W Sellors are lovingly and securely dispatched with our elegant jewellery packaging. Matching items also available within this collection.