Mention the word "gemstones" and it immediately brings to mind images of glittering riches. Gems have been a byword for wealth in popular culture for hundreds of years. So it isn't surprising that many people think the gemstones that are most well known today - rubies, emeralds, diamonds and sapphires - have always been the most valuable. But the history of gemstone valuation is not so straightforward.
Instead, we find that the historical desirability of various gems was dependent on a range of factors, including local availability, rarity, physical properties and, oddly enough, advances in science. In his book "Natural History" written in the 1st century AD, the ancient Roman naturalist Pliny the Elder states that agate, a banded variety of quartz, was "formerly held in high esteem, but is not so now… (because it) has since been discovered in numerous other localities." This is, to the best of my knowledge, the first example of a once rare precious gemstone being devalued when new, large sources of material were discovered.
Agate wasn't alone in this misfortune, either. All members of the quartz group, such as cornelian, chalcedony, jasper, rock crystal and amethyst, were highly valued in ancient times. But they gradually declined, in both respect and price, over the centuries as new deposits were exploited and long distance trade routes from Asia and sub-Saharan Africa expanded. By the Middle Ages, the quartzes were no longer considered top tier gemstones in Europe.
There was one notable exception to this, however. Amethyst, with its maddeningly deep purple hue - the same color valued so highly by royalty - remained a very expensive stone into the 16th century. During the Renaissance, fine Indian amethyst traded for fully half the price of precious sapphire.
But the Age of Discovery, the period from the 15th to the 18 century when European explorers sailed to all corners of the globe in search of new lands, was not kind to the reputation of many gemstones. Amethyst, the most valuable of all the quartzes, was one of those gems negatively affected. Although it remained relatively scarce until the early 19th century, massive Brazilian discoveries flooded the market in the 1830s and 1840s, causing the value of amethyst to collapse. Its price never recovered. Even today it is possible to buy good quality amethyst for only a few dollars a carat.
Another ancient stone undone by the advancement of science was the highly prized carbuncle. In ancient Greece and Rome, the term carbuncle referred to any deep red gem. It is theorized that garnets, rubies and red spinels were all interchangeably considered carbuncles during this period. However, as science progressed, it became obvious that these gems were actually distinct types of stones with unique physical properties.
This caused a divergence in the prices of these gems types. Garnet, being softer and more common than its two look-alikes, rapidly dropped in value, while the superior ruby became the gem of kings. However, ruby and red spinel, which are closely chemically related, were still confused with one other right into the early 19th century. It was only after this time that the two doppelgangers were definitively, scientifically recognized as separate gems. Subsequently, many famous "rubies" set in the crown jewels of European monarchs were discovered to actually be red spinels, thus boosting the reputation and value of real rubies even more.
Some things in the world of gemstones, though, have remained fairly stable for centuries. Benvenuto Cellini, a renowned Italian Renaissance goldsmith from the 16th century, wrote in his memoirs that ruby was considered the most valuable of all gems. Next was sapphire. Diamond, although far rarer during the Renaissance than today and largely reserved for nobles, was only ranked third. During that period, a fine diamond was only worth an eighth of what a similarly high quality ruby would bring.
Cellini's list of relative gemstone valuation compares favorably to our "big four" gems of today, which are, in order of descending value: ruby, emerald, diamond and sapphire. But even these rankings are a closely fought thing. Emeralds and rubies have vied with each other for the top spot throughout the 20th century, trading place several times. And white diamonds are just barely holding onto the number three slot. Currently, a top quality, one carat, Burmese blue sapphire is nearly equal in value to a flawless, perfectly colorless, one carat diamond.
The latest development in the long history of gemstone valuation has been the rise of new, ultra rare gems. These include stones like colored diamonds, alexandrite, demantoid garnet and Paraiba tourmaline. All of these "new" gems are exceedingly beautiful, extremely rare and often exorbitantly expensive. It is not unusual for fine examples of these stones to exceed the "big four" gems in terms of price per carat - sometimes by significant amounts.
Although fancy colored diamonds were known for centuries before the modern era, they were so rare and unusual that they were thought of as curiosities for most of that time. Both alexandrite and demantoid garnet, first discovered in the mid 19th century, likewise remained exotic oddities for many decades. It was only in the late 20th century that these extraordinarily rare stones, along with more recently discovered ultra rare gemstones like Paraiba tourmaline, have become quintessential luxury objects gracing the fingers and necks of billionaires around the world.
Although gemstone valuation has been constantly evolving over the last two millennia, I believe we have reached a point in history where major re-rankings will now occur much more slowly. Most of the world's major gem fields have been discovered already, so it is increasingly unlikely that the market will suddenly be flooded by a large quantity of any given gem. Science has also progressed to the point where different types of gems are no longer confused with one another. Of course, relative gemstone valuation will continue to change in the future as certain colors or looks fall into or out of style. But I think the chances of major gems, like ruby, sapphire or emerald, devaluing severely are nil.
