A gemstone is a crystalline material valued for the combination of beauty, exceptional durability, and rarity. The majority of gemstones are minerals, with a few exceptions of organic origins, like pearls, red coral, and amber. There are even gemstones of extraterrestrial origin. Among 4000 natural minerals, only less than two dozen are commercially significant gemstones. A gemstone's beauty comes from its color, "fire," iridescence, opalescence, asterism, chatoyance, unique pattern or inclusions, and luster. A gem also has to be durable to withstand handling, polishing, and setting.
How Are Gemstones Priced?
A gem's value is defined by evaluating its physical and optical properties known as "Four C": color, clarity, cut, and carat. But the grading system is not as rock-solid: different experts can all disagree on the qualities of the given gemstone. Eventually, the price of a gem ends up being determined subjectively through an agreement between a specific buyer and a seller. For collectible gems, rarity and size play the most critical role. History matters, too: a gemstone becomes much more expensive for its provenance.
Blue Diamonds occur when boron atom substitutes carbon in the crystalline lattice, producing an effect of the selective absorption of red light and transmission of blue. It is an extremely rare event, as it requires enormous powers. Blue diamonds are so unique that they each receive their names. The most legendary diamond of all is the Blue Moon Diamond sold at $4 million per carat.
Red, Orange and Pink Diamonds
Red, orange, and pink diamonds selectively transmit the red light thanks to the change in the placement of their glide planes due to forces deep within the Earth. Each carat of The Pink Legacy costs $2.6 million; Moussaieff, a stunning Red one, is next with over $2.4 million per carat. A vivid pink diamond, The Pink Star (renamed "The Winston Pink Legacy" by the new owner), became the most expensive gemstone ever sold due to its enormous size, almost 60 carat. It took two years to study and cut to reveal its beauty without sacrificing the size, and the final price was $71.2 million.
Ruby is a red or purple-red variety of the mineral corundum. Their red colors and soft, noble glow in artificial lights gained them recognition as a symbol of passion, power, and life. Yet, it took them a long time to join diamonds in the ranks of gemstones of over $1 million per carat. In 2015, The Sunrise Ruby, a Burmese Red ruby, sold for $30.42 million thanks to intense color and incredible purity rare in ruby of over 20 carats.
These recognizable green specimens of the mineral beryl present their challenge that impacts the price: stones without imperfections or inclusions are scarce, so flawless emeralds are valued much higher. A "Rockefeller Emerald," the 18.04-carat gem, was sold for $305,000 per carat. Emeralds also have lower density and hardness than diamonds, and, although they are durable stones, emeralds are susceptible to chipping and cracking; well preserved historical emeralds are sought after.
Sapphire is another variation of the mineral corundum, the same as ruby. Naturally bright color, high clarity, and large size make for a stunning - and very expensive - Sapphire. A rare type of sapphire, padparadscha sapphire, is pink-orange. The blue variety is truly a Royal gemstone: both Princess Diane and Queen Elizabeth II preferred sapphire and diamond sets for important occasions. The Jewel of Kashmir Sapphire of a stunning cornflower blue color was sold for $6.7 million, just under $250,000 per carat.
This rare type of chrysoberyl deserves its nickname "emerald by day, ruby by night." It is adored for its remarkable color-changing ability, produced by trace amounts of chromium: it appears blue-green in sunlight and purple-red under artificial light. The more apparent the effect of the color shift, the more valuable the stone is. The Smithsonian has the largest known faceted 66-carat Alexandrite on display in their museum, and the highest cost obtained was $70,000 per carat.
Painite, Taaffeites, and Musgravite
These gemstones got their place among the most valuable thanks to their rarity. Only a few hundreds of red-brown painite stones have been faceted. Myanmar remains the only place that mines these crystals, and the price rises to $60,000 per carat. The very first stone of the warm-hued Taaffeite was found already cut and faceted "hiding" in a box of a similarly colored Spinel stones in Dublin. Musgravite is a close relative of Taaffeite sporting grey-purple to olive green hues. Their scarcity affected the price tag: both cost up to $35,000 per carat for exceptionally beautiful pieces.
Spinel comes in many vibrant colors with a very special luminance. Red spinel is the most desirable, followed by cobalt-blue, hot pink, and vivid orange stones. Spinels and rubies have a very similar formula, but ruby has a trigonal crystal structure, while spinel - cubic, like a diamond; this explains why spinel has a crisp shine, while ruby glows. Many famous stones recorded as "rubies," including majestic gemstones in several European crowns, are, in fact, red spinels. In 2015, the Hope Spinel gemstone got sold for $30,000 per carat.
This gemstone can be considered the most valuable newcomer, as it was discovered in Madagascar a mere 22 years ago, in 1998. Before that, Garnet was thought to come "all colors but blue." What makes this stone even more desirable is that it is a pronounced "color shifter," just like Alexandrite: under different types of light, it shines in blue or purple-pink. A 4.2 carat stone was sold for $6.8 million in 2003, but the price might change if more locations to mine these gems are discovered.
Jadeite is the brightest, the rarest, and the strongest of all jades. Its value is multiplied by its historical and cultural significance. The first finds of artifacts can be traced back thousands of years to the Mesoamericans. It plays a vital role in Chinese culture as a symbol of prestige and status: the most valuable, green, and ice green varieties are called Emperor Jade. Because of its excellent properties for carving, many jadeites were turned into unique and precious pieces of art. The most expensive jewelry item, Hutton Midivani necklace, was auctioned for $27 million.