Gemmological and metallurgical research on the Cheapside Hoard, the largest cache of Elizabethan and Jacobean jewellery in the world, is helping to transform our understanding of the working practices, manufacturing techniques and craft-skills of the early-modern goldsmith-jeweller and London's role in the international gem and jewellery trade.

In December 1775 Francis Mouzin and John Keyser were found not guilty of stealing a large haul of gems from Joseph Dermas, including ‘fifteen carats weight of diamonds for glaziers’, ‘five carats weight of diamond powder', five hundred carats weight of rough rubies’, ‘one hundred cornelian stones’ as well as ‘antique diamonds’. This evidence from the Old Bailey Proceedings reveals gems and jewellery literally in transit, but captured in the wording of the indictments. This paper is a preliminary attempt to assess the value of this source as a means of understanding the different languages of description and valuation, of places and persons from which gems and jewellery were taken, and what happened to them between owners both legitimate and not.

Experimenters were avid consumers of gems in the long eighteenth century. They did not simply display their precious and semi-precious stones in mineral cabinets. They heated them, rubbed them, weighed them, pressed them with sharp objects, shone rays of light through them, dissolved them in acid and burned them with sunlight focussed by mirrors. They did so in the hope of improving mineral classifications and of understanding light, colour, heat and electricity. These experimenters were not always consumers in the strict sense—they did not always buy the gems they experimented upon. But they were consumers in the larger sense that they went to considerable lengths to acquire gems, made intense use of them, and communicated their experience of gems to other consumers in the hope of influencing their purchasing decisions. This talk focuses on experimenters based at the Académie Royale des Sciences and the Jardin des Plantes (later the Muséum National d'Histoire Naturelle). Key individuals are René Réaumur, Charles Dufay, Louis-Jean-Marie Daubenton, Alexis-Marie de Rochon, Antoine-Laurent Lavoisier, Mathurin-Jacques Brisson, and René-Just Haüy.