I am assuming that by “chain” Pomellato means necklace but it’s difficult to tell the dimensions from their photo. Tilda Swinton is the face of this new and aptly named Victoria collection. Jet is fossilized bog oak. The Whitby, England area became famous for it when mourning jewellery became popular following the death of Queen Victoria’s consort Albert, and the period of prolonged mourning that followed. It is fairly lightweight, being wood, and polishes to a glossy shine.

Pomellato has paired jet with rose gold and I really like the contrasting textures and colour. See the Pomellato site for “where to buy“.