Silver Whitby Jet Marcasite Thirteen Stone Drop Triangle Necklace. N995. This stunning statement piece features a large triangular shaped hand carved Whitby Jet gemstone as the focal point, with additional triangle shaped Whitby Jet gemstones along the length of the necklace, alternating between Marcasite set circles. Each stone is framed in Sterling Silver and accented with sparkling Marcasite gemstones for a beautifully ornate and vintage feel. All our Whitby Jet jewellery is designed and crafted within our very own workshops in Ashbourne, Derbyshire where a team of skilled craftsmen turn the raw Whitby Jet stone into these stunning pieces of jewellery. You can find other matching Whitby Jet jewellery and other Whitby Jet necklaces online and instore. Silver Whitby Jet Marcasite Thirteen Stone Drop Triangle Necklace. Large Whitby Jet stone 24mm x 18mm, Small Whitby Jet Stones; 10mm x 8mm, necklace length; 16 inches.