Jet is the fossilised remains of driftwood. In Britain, the main source is Whitby, in Yorkshire. It became particularly popular in mourning jewellery in the mid 19th century.
The custom of wearing mourning dress was encouraged by Queen Victoria’s prolonged mourning after the death of her husband Albert in 1861. Formal mourning required black crepe or bombazine clothes along with ‘a few trinkets to accentuate the general sombreness of the costume’. This tiara shows that jet or its substitutes was worn at the highest level of society: only those above a certain social class would have had the occasion to wear a tiara. It is interesting that it is made of ‘French jet’, a cast glass substitute for jet. As supplies of jet were not sufficient to keep up with the demand, dark cast glass known as ‘French jet’ or ‘Vauxhall glass’ was often used.