Topazes, Emeralds, and Crystal Rubies. The Faking and Making of Precious Stones

Marjolijn Bol

Today the making and illegal selling of factitious stones has reached an unseen level of sophistication. Advanced technologies allow man to produce synthetic versions of the most precious of stones – diamonds, emeralds, sapphires and rubies (fig. 1). So convincing are these synthetic gems they can only be distinguished from natural precious stones in laboratories with advanced spectroscopic devices.

Fig. 1 Synthetic gemstones
Fig. 1 Synthetic gemstones

The making of imitations of precious stones is not just typical of our modern age. In fact it dates back to at least Egyptian times, as graves from this period show that glass was used to substitute for jewels. Seneca (AD 1 – AD 65) and Pliny the Elder (AD 23- AD 79) were the first authors to write about the practice. Whereas Seneca only mentions that ‘sometimes stones are boiled to resemble emerald (smaragdus)’, Pliny provides us with a rather lengthy account in which he explains the various ways in which gems were imitated. He mentions that glass pastes were used for the imitation of seals and that in some cases stones were cemented together to imitate sardonyx. By a third method, ‘Indian crystals’ were colored with certain dyes to make them look like more expensive minerals. These ‘gems’ were apparently so convincing that ‘(…) there is considerable difficulty in distinguishing genuine stones from false; the more so, as there has been discovered a method of transforming genuine stones of one kind into false stones of another.’ While some physical evidence still survives of the first two practices, the factitious gems made by the third manner, has barely, if at all, come down to us. The many recipes that explain how to make such imitation stones (surviving from the fourth well into the sixteenth century) nevertheless suggest that this last method must have also been practiced, and perhaps even on a large scale. I therefore hoped that a physical reconstruction of the imitation gems might give some further insight into the appearance of these imitation gems. Would it be possible, as the recipes suggest, to make a convincing imitation of a precious stone? Could such a ‘fake’ potentially fool the innocent eye into thinking it was real?

The earliest examples of recipes for imitating stones can be found in the so-called Stockholm Papyrus, a recipe collection written in Greek at about 200-300 AD. The Papyrus includes no less than 71 how-to’s for the imitation of precious stones with lesser materials, including ruby, beryl, amethyst, sunstone and emerald. In subsequent centuries, numerous other recipe books include similar instructions for making counterfeit stones. While the recipes are various, they are almost all based upon two basic operations that I have attempted to reconstruct (fig. 2).

Fig. 2 Opening up of stones
Fig. 2 The opening up of stones

First, a transparent mineral, such as rock crystal, selenite, or topaz, is roughened or ‘opened up’. Following the recipes instructions, I investigated this by cooking the minerals in potash alum (potassium aluminium sulphate) dissolved in vinegar. As soon as I removed the heat from this mixture, it rapidly crystalized into a hard crust around the stones. In accordance with the recipes I left the stones overnight.  Nevertheless, when I inspected them the next day (after having chiseled them out) I could not see any changes. Regardless of whether the stones were successfully ‘opened up’, the coloring of the minerals did produce some surprising results.

The recipes instruct that the ‘opened up’ mineral should be colored using a mixture of a colorant ground with oil or resin to make it assume the appearance of a specific gemstone. The dyes and pigments used varied according to the type of gemstone that was to be imitated. A red dye made from alkanet root (used by ancient cloth dyers) was advised for the imitation of rubies and the green copper pigment verdigris was used to transform transparent minerals into emeralds. For my first reconstructions I choose to make a ‘fake’ emerald. It was one of the precious stones imitated the most frequently and the instructions for making it remained almost the same through (post-) classical and pre-modern times (fig. 3).

Fig. 3 Coloring of stones
Fig. 3 The coloring of stones

I first ground the pigment verdigris with linseed oil and used this substance to cover the base of a rock crystal, topaz and piece of selenite. This resulted in a beautiful, translucent green stone that, due to the instability of the pigment verdigris, in time assumed the saturated forest green color of a real emerald. Whereas more reconstructions are certainly required to investigate the nature of this method of gemstone imitation, these first experiments show that, when ancient sources insist how visually convincing the imitations of precious stones could be, they are probably not exaggerating.

Fig. 4 Emerald imitation
Fig. 4 Emerald imitation

Recommended reading:

Marjolijn Bol, ‘Coloring Topazes, Crystals and Moonstones: The making and meaning of factitious gems, 300-1500’, in Marco Beretta and Maria Conforti (eds.), F for Fakes: Hoaxes, Counterfeits and Deception in Early Modern Science, 2nd Watson Seminar in the History of Material and Visual Science, Museo Galileo, Florence, June 7, 2013, Science History Publications (Brill Publishers: 2014), pp. 108-129.

Earle R. Caley, “The Stockholm Papyrus: An English Translation with Brief Notes”, Journal of Chemical Education 4 (1927), pp. 979-1002.

Pliny, The Natural History, books 33-37 (book 36 includes Pliny’s natural history of stones): http://www.perseus.tufts.edu/hopper/text?doc=Plin.+Nat.+toc


4 thoughts on “Topazes, Emeralds, and Crystal Rubies. The Faking and Making of Precious Stones”

  1. Incredible!

    Thank you very much.

    I am a medieval recreationist (SCA) who has been seriously interested in gemstones and jewelry for several years (not to mention pirate treasure and wizard’s magical stones from my childhood!). My recent reading has included works by Pliny, Albertus Magnus (Dorothy Wyckoff), as well as medieval lapidaries. Yesterday I came across a reference in Wyckoff to a book by Mary Merrifield (Original Treatises on the Arts of Paintings, 1849, reprint 1967), which my library happened to have. Volume II of Merrifield includes a fifteenth century manuscript with several recipes (pp. 506-524) similar to the one you used. Of course, as a recreationist I am not satisfied to simply read about these things–I want to make my own!

    Your experiment is an inspiration to me, given its relative simplicity. One does not a glass furnace to make these things, after all.

    Finally, given your experiment, you might be interested to know that rock crystal is used in several of these recipes, both in ground form and as a base gem to be dyed.

  2. By the way, could you post the proportions of the materials used?

    Thanks.

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