In jewelry beware of false friends. Or rather, do not buy stones that have different value, but a similar appearance. Similar, but not the same. Yet, in the misunderstanding there have falls for not only authoritative gemologists, but also customers willing to pay figures with many zeros and even crowned heads. Do you want an example? Numerous precious stones belonging to the treasure of Tsar Peter I of Russia, believed to be rubies for a long time, were later classified as rubellite. The same gem, the ruby, has also deceived the royals of London: the so-called Ruby of the Black Prince of about 170 carats mounted on the British imperial crown is not a ruby, but a spinel, placed near the Cullinan II diamond, this authentic.
But how can such a sensational exchange of precious stones happen? Well, it was once easier: gemology was not a developed science and there were no instruments capable of measuring the light waves refracted by the stones used in jewelry. Even today, however, many vintage jewels may have mounted stones that do not correspond to those attributed. And, therefore, the value of the jewel can change dramatically. In short, beware of false friendships: as in life, even for jewelry they can be dangerous.
Ruby and spinel. Both are red stones, although the spinel can also take on other shades. The spinels that have clarity and transparency of gems resemble ruby and sapphire. Not only that: it is often found in deposits adjacent to those of these two most precious stones. In addition to the deep red spinel, there is also a raspberry-colored variety that is extracted in Tanzania.
Ruby and rubellite. Rubellite is another red stone, which can have an intense hue similar to that of certain rubies. It is, however, a variety of tourmaline. Rubellite was already known by the ancient Romans and often the gem was confused with garnets and spinels. The great diffusion in the West occurred at the beginning of the seventeenth century after the importation by the Dutch from Sri Lanka. And today: in 1998 a large tourmaline mine was discovered in Nigeria and rubellite invaded the jewelers.
Spinel and taaffeite. It is taaffeite that is rarer and more expensive. Taaffeite is named after its discoverer, the Irish Richard Taaffe, who in 1945 identified it confused with other spinel gems. Shipped to London for analysis, it was identified as a new gemstone, unfortunately very difficult to find. Unlike spinel, taaffeite shows the property of double refraction which allows the distinction between these two minerals. It can have different colors, including violet red and red, which make it very similar to certain varieties of spinel.
Diamonds and zircons. Attention, let’s not talk about cubic zirconia, which are artificial stones with a very low price and used for pendants and bijoux that cost a few tens of euros or dollars. Zircons are natural stones. They may have different colors, but in the colorless variety it is very similar to diamond. Zircon, in fact, has a very high refractive index, lower only than that of the diamond, and for this reason it has often been mistaken for the gem it resembles. From a chemical point of view, however, diamonds and zircons are different: the former are made of pure carbon, the latter are nesosilicates.
Emerald and demantoid garnet. They are two green stones. Demantoid garnet, just like emerald, takes on a green hue due to the percentage of chromium and iron, which lead to bright green hues or more tending to green-yellow, also green tending to blue. Another garnet variety, tsavorite, also has a green hue that can be mistaken for emerald. In fact, many jewelers combine the two stones on the same jewel to lower the cost.
Topaz and quartz. Sometimes white or lightly colored topaz on the yellow is exchanged for smoky or citrine quartz. Obviously a simple quartz costs less than topaz.