18ct Yellow Rose Gold Whitby Jet Diamond Lyria Necklace. CMT116. This unique marquise shaped Whitby Jet and Diamond drop pendant is set in 18ct Rose and Yellow Gold. A subtle 0.03 carat diamond adds unique detail to the clasp, this pendant is a sophisticated and stunning design featuring Whitby Jet stone which has been sourced directly from the North East coast of Yorkshire. 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. 18ct Yellow Rose Gold Whitby Jet Diamond Lyria Necklace. 18 inch long chain, pendant drop 35mm, Whitby Jet; 15mm x 5mm.