Good morning Tanjila Thank you for the images! Jet was used in Victorian mourning jewelry. The cameo relief depicted is more than likely playing cameo role and subject of mourning.
Jet is a form of fossilized wood, halfway between peat and bituminous coal. During the Victorian era the principle source of jet was from mines in Northern Yorkshire, in the town of Whitby. This is where the jet carver's art flourished in the mid-nineteenth century. Today the main sources of good quality "hard" jet are Spain, France, Germany, the former USSR and Utah in USA.
The five main simulants of jet are moulded glass known as French Jet or Vauxhall glass, vulcanite, plastics such as Bakelite and expoxy resins and black-stained chalcedony.
French jet has a higher SG and harder (6.0 on the MOHs scale) than jet. It also is colder to touch and may contain "bubbles". Chalcedony can be identified by its greater hardness, lower RI and its coldness to the touch.
