Treated And False Stones

(via Roman Book On Precious Stones: 1950) Sydney H Ball writes:

In Pliny’s time, stones were treated to improve their appearance and the art of making paste imitations of gems advanced.

To paraphrase him: All precious stones are improved in brilliancy by being boiled in honey, Corsican honey in particular; acrid substances, however, are injurious to them. (If by ‘boiled’ Pliny means heated, he had the secret of artificially coloring agate; if not, his informants were holding out an essential step in the process). Such treated stones, to which man has imparted new colors, are called physis (‘nature’ or ‘works of nature’), a bit of deception, since dealers recognize that products of nature are more sought after than those of man.

The above free rendering may be a rather obscure reference to an art, which the Hindus even then doubtless practiced, of improving the color of varieties of the cryptocrystalline quartz species by exposure to the sun or to fire, after permitting the more porous layers to absorb honey or other liquids. It is, therefore, believed that the Romans knew something of agate staining. Barbosa (1517 A.D) describes the art and it doubtless long antedated his time. Could the line in Propertius (flourished 30 to 15 B.C) regarding murrha (agate in part) ‘And murrhine vessels baked in Partian hearths’ refer to this process?

The ceraunia, on the other hand, is temporarily improved by being treated for some time in a mixture of vinegar and nitre, and the brilliancy of poor garnets is heightened by steeping for fourteen days in vinegar, the improvement lasting an equal number of months.

Pliny states that books exist which tell how to counterfeit precious stones, but he ‘refuses to name’ the authors, evidently to protect the owners of real gems. This reminds one of David Jeffries’ lament (1750 A.D) when the brilliant cut was supplanting the rose cut diamond, that, provided the ‘fad’ continued, the nobility of England, being large possessors of rose cut diamonds, could be ruined. An earlier analogue is that of the Chinese ambassador, Kan Ying, who reached Antioch, the capital of Rome Syria, in 97 A.D. ‘The articles made of rare precious stones produced in this country are sham curiosities and mostly not genuine, whence they are not (here) mentioned’. Regarding gem counterfeiting, Pliny adds that there is no deceit practiced, which is more profitable. He recognizes that the best method of testing a false stone is to break off a fragment and test its hardness, but the Roman jeweler would not permit this nor the use of the file. In other words, Pliny recognized that hardness is one of the best gemological tests.

As happens today, less valuable stones were palmed off for the more valuable species, and Pliny states, as is the case today, this is a particularly difficult deception for the layman to detect. Sardonyx was imitated by a triplet of a black, a white, and a red stone, each of excellent quality, cemented together. Martian (40-104 A.D), in describing a fine jewelry shop of his day, mentions ‘real sardonyx, indicating that false exists. In Pliny’s time, crystal was stained to imitate emerald and other transparent stones, and other frauds were perpetrated. The people of India, by coloring crystal, imitated various precious stones, particularly beryls. Perhaps the process by which Democritus imitated emerald resembled that of Indian crystal imposition. He discovered, Seneca says, how a pebble can be transformed into an emerald by boiling it. By a similar process artificial gems are stained today. From the Hindu poem Hitopedesa (dating from about the time of Christ), we quote the following lines, more or less detached, to be sure:

‘Silly glass in splendid settings, something of the gold may gain;
And in company of wise ones, fools to wisdom may attain.’
‘Glass will glitter like the ruby, drilled with dust—are they the same?’

An ancient Hindu play Mrichchhakatika or Little Clay Cart (6th century A.D?), as to Hindu makers of false stones, says ‘they readily fabricate imitations of ornaments they have once seen, in such a manner that the difference shall scarcely be discernible’.

Returning to Pliny, he says that any color can be imparted to amber that may be desired, it being sometimes stained with kid suet and root of orchanet; indeed, in his day, amber was even dyed purple. Much amber was used, he says, to counterfeit gems, especially amethyst. We may add that today pressed amber is successfully colored.

The artisans of Pliny’s time imitated many stones in glass and some of these false gems which have come down to us would test the skill of an expert of today. Certain Italian jewelers still, after recutting, sell as real gems the pastes dug up in Rome. Obsidian, murrha, crystal, and other stones were imitated. Pliny states that glass imitations of jasper are easily detected and as to opal, it is the most perfectly imitated, although the opalescence is partly or largely lacking. The callaina (turquoise) is also successfully counterfeited. Genuine capnias is much colder than the glass imitations. Carbunculus (garnet and other red gems) is well counterfeited, but the glass imitation is softer, comparatively brittle and lighter in weight. Further, the inclusions differ. The Egyptian cyanos is undoubtedly a blue frit, an imitation of turquoise.

The Egyptians and the citizens of Ur made glass imitations of gems some 5000 years ago. Later (1600-1400 B.C) the Myceneans were adept at the trade. On the other hand, while there are a few Greek paste intaglios of the 4th century B.C, such were rare before the 3rd century B.C. Pastes were much used in Rome until some years after Pliny’s time, when they became less common, probably because genuine precious stones were in large supply. Glass in Pliny’s time furnished the poor, who could afford gems, not only with the ‘costume’ jewelry of that day, but with a necessary signet. Paste in those days was, from its decorative value, ranked nearer to precious stones than it is today, for the faceting of stones, which brings out the full beauty of the transparent gems, was then in its infancy. Further, in those days, glass was a much more scarce and precious substance than it is today, so that its use in jewelry was less culpable than today. Alexander Severus, in attempting to stamp out the luxury of Heliogabalus’ reign, placed heavy taxes on the glassmakers. Diocletian (Emperor, 284-305 A.D) decreed that all books describing the synthesis of gold and silver and the fabrication of artificial precious stones should be burned.

There is a thought-provoking statement in Horace, namely, crystal vases ‘had been spoiled by an admixture of glass’. The Romans, in the writer’s opinion, could scarcely have melted rock crystal and glass together.

I think we can all smile with Emperor Gallienus, who reigned from 260 to 268 A.D. A jeweler had sold Gallienus’s wife, the Empress Salonina, false gems for true. She called the matter to the attention of the emperor and he immediately ordered the jeweler to be thrown to the wild beasts in the circus. Naked, the poor wretch stood in the arena awaiting his doom. The door of the wild beasts’ den was thrown open; out strutted a rooster! The emperor’s comment, ‘he who had cheated others should be cheated himself.’ More militant punishment is recommended in the Hindu Agastimata (16th century), as follows: ‘The vile man who fabricates false diamonds will sink into an awful hell, charged with a crime equal to murder.’

One of the last parts of Book XXXVII is an excellent and, to all intents and purposes, a modern summary of the methods of testing gems. This has already been quoted in the section on Pliny as a mineralogist. In short, glass imitations are lighter, better conductors of heat, contain more gas inclusions, and are softer than gemstones.