BY JEAN-LOUIS LEFERRE (FL. 1803-1822), MARKED, PARIS, 1809-1819, WITH THE PARISIAN THIRD STANDARD MARK AND EXCISE MARKS FOR GOLD

Chrysoprase was used as a decorative stone by both the Greeks and Romans and is the most valued variety of chalcedony. The colour derives from the presence of nickel which can fade in sunlight and be confused with jade. The best chrysoprase was mined in the 18th and 19th centuries in Poland and Czechoslovakia. One original manufacturing process for goldstone was invented in 17th century Venice by the Miotti family, who was granted an exclusive license by the Doge. Urban legend says goldstone was an accidental discovery by unspecified Italian monks or the product of alchemy, but there is no pre-Miotti documentation to confirm this. Another common name for the material is 'aventurine glass', based on the original Italian name aventurina.