False Precious Stones: Semi-Stones or Doublets

This mode of imitating real stones, though varying in a great many respects, is generally effected by giving the proper shape to a morsel of strass; removing from the upper portion of it a certain thickness, and replacing this by hard stone in such a way as to complete exactly the strass stone, then mounting the whole in a setting that completely conceals the line of junction of the two stones.

Doublets are of two kinds: in both the under part is strass, but in one the upper part is a plate of the real stone; in the other, it is simply hard stone, generally quartz, and of no value.

The invention of this process has been attributed to a modern jeweller of Paris, named Bourguignon; but in reality it can be traced as far back as the fifteenth century.

A complete description of the mode of manufacturing doublets is given by Cardan, who has even preserved for us the name of the inventor:--

"A fraud of a very bad character, and one very difficult to find out, was employed by Zocolino--. This venerable personage used to take a thin flake of real precious stone, such as carbuncle, emerald, &c., when he wished to imitate the carbuncle or emerald, choosing such pieces as had but little colour, and were consequently very cheap. Underneath he placed a piece of crystal sufficiently thick, and united the two parts by means of a transparent glue, in which he incorporated a colouring matter in harmony with the stone that he meant to imitate--brilliant red for carbuncle, green for emerald, &c. He concealed the line of junction of the two parts by means of the setting; and to avoid giving rise to suspicion, he set them in gold, which was not allowed except in the case of real precious stones.

"In this way this magnificent workman deceived everybody, even the lapidaries. However, the fraud was at last discovered, and Zocolino took refuge in flight.

"It appears that this personage had a peculiar disposition for fraud, for he turned his attention afterwards to the fabrication of counterfeit money; and ended by being condemned to death."