(via The Journal of Gemmology, Vol.13, No.8, October 1973) J M Ogden writes:
Since the brief note on Roman imitation diamonds by the writer was published in the Journal of Gemmology two fine Roman rings, both set with interesting stones have been available for study. The first has an attractive openwork-sided setting in which is set an octahedral stone. This stone was at first glance taken to a rock crystal of the type considered by the writer to be a Roman imitation of a natural diamond crystal. Closer inspection of the stone however revealed the typical surface decomposition characteristics of glass and the stone was, in fact, a yellowish white glass (the term paste would be wrong here, as technically this should only refer to those glasses with high refractive index and brilliance). The writer knows of other instances of rings set with glass octahedral, and these, like the rock crystals, might be taken to be imitations of diamond crystals. It might be argued that any reasonably knowledgeable Roman could have told glass from the invincible diamond, but one would expect that these copies of diamond crystals were more in the nature of moral frauds; in other words they would have been worn by those to whom the diamond was, for reasons of economy or rank out of reach. A similar state of affairs can be seen earlier in the Roman period when only free-born citizens were allowed to wear gold rings; slaves and others made do with wearing gilt bronze rings.
The second ring is extremely interesting and possibly even unique, as it is set with a brown diamond. This stone, larger than any other Roman diamond known to the writer, is in the form of rough natural twin octahedral. Alec Farn of the Gem Testing Laboratory very kindly examined and tested this stone and found it to be a brown-series diamond: two lines, at 4980 Angstrom, were visible in the spectrum, and there was a blue fluorescence under X-rays. The weight of the stone was difficult to gauge, but it must have been about 7 carats. The majority of the Roman diamonds known to the writer do not have recorded weights, but they generally would seem to weigh under a carat. This large stone under discussion was by no means obviously a diamond from color or appearance, except to one versed in crystallography; so other stones of a similar nature might exist, unrecognized, in museum or private collections. In its recent history the stone in this ring has been described in a multitude of ways, most recently as ‘Topaz’. This fine ring is of a similar type to the first ring mentioned above, although it is sturdier and its size would indicate that it was definitely a man’s ring. Both these rings were originally in the collection of Count Henri de Clercq Boisgelin, a well-known collector whose ancient jewelry included some of the finest specimens known. There is no cause to doubt that both these rings are genuine, and that they date from the late Roman period (c. 3rd - 4th century A.D). Close examination by the writer revealed no evidence that the stones were not originals: indeed the ring holding the diamond had quite obviously been made for that stone and none other. The coloration, surface appearance under strong magnification and the general ‘feel’ of the gold in both cases would show that the settings were as old as supposed.
No provenance is recorded for either of these rings, though it would seem likely that they were made in Italy or in one of the Eastern Roman centers such as Asia Minor or Egypt. The exact area of origin for the diamond is not known, but it would be likely that it was traded ‘loose’ from India, possibly via Alexandria.
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