A Glittering Guide to Birthstones

B illions of years in the making, diamonds are one of nature’s most wondrous and precious gifts. After being formed in the earth under immense pressure and heat, precise cutting and polishing bring out their incomparable beauty. While one could feast her eyes on beautiful diamonds at virtually any jewelry store, only the most perfect ones – think 100-plus carats and incredibly rare colors – reach stratospheric prices at auction. For example, the CTF Pink Star set a world auction record for any diamond or jewel when selling at Sotheby's Hong Kong in 2017.

O nce Cleopatra’s alleged favorite gemstone, the glamorous emerald continues to impress everyone from royals to the red carpet’s best dressed. Beloved for their rich, exotic color, emeralds are a bluish-green variety of the mineral beryl. When chromium, vanadium and iron are present in beryl, emeralds form, and the varying presence of these three elements results in a range of colors. If the stone’s hue is too yellow or blue, it is not an emerald but rather a variety of beryl, which makes highly transparent and vividly saturated green emeralds extremely valuable and coveted.

I n 1917 Pierre Cartier famously traded a double-stranded, natural pearl necklace, valued at the time for $1 million, and $100 in cash for a mansion on Fifth Avenue, where he established Cartier New York. Pearls have always exerted a powerful allure. Worn by royalty, legendary beauties and style icons – just think of Audrey Hepburn's pearl-and-diamond statement necklace in Breakfast at Tiffany's or Coco Chanel's signature layered strands, still a staple in the fashion house's runway collections today. Unlike diamonds, natural pearls emerge as finished gems, and the finest are lustrously silky and perfectly round, which makes finding a match an incredible feat. In 2018 Sotheby's sold a pearl pendant formerly in the collection of Marie-Antoinette for CHF36,427,000 – more than 18 times its high estimate and a new record for a natural pearl.

R ed: the color of passion and power, fire and blood. With its symbolic significance and radiant hue, the ruby is among the most valuable and commanding precious stones. Whether in ancient India, medieval Europe, or the Golden Age of Hollywood, different eras have coveted rubies not only for their hardness and durability, but also their associations with vitality and wealth. Virtually identical to sapphire in all properties except color, ruby is a variety of the corundum mineral species. In its purest form, corundum is colorless, but the trace element chromium produces the red tone. While richly toned gems like garnet and spinel are often mistaken for the stone, genuine rubies are far rarer and more valuable.

W ith remarkable clarity and high double refraction, it’s no wonder the Egyptians referred to peridot as the “gem of the sun.” Although they were often mistaken for emeralds, take Cleopatra’s prized, allegedly emerald jewel collection for example, peridots are downright fascinating, even considered extraterrestrial gems. They’ve been found deep in the earth’s mantle, ancient meteorites, comet dust, lava and volcanic rock, a rich source of magnesium and iron, the element behind that distinct yellow-green color.

R ich in color, superb in quality and perfect alone or paired with virtually any gem, sapphires have universal appeal. Belonging to the mineral species corundum, of which ruby is another variety, sapphire is most associated with blue – arguably the most famous such stone being Kate Middleton's and Princess Diana's engagement ring – but it comes in a rainbow of hues. Sotheby’s has sold some of the world’s most jaw-dropping sapphires, including Royal blue rarities from the Kashmir mines and valuable pinkish-orange varieties known as padparadscha sapphires.

S tunning as a single pop of color on a statement brooch, or in a multi-stone piece that showcases the stone’s iridescence, the opal always makes a strong statement. Many Art Nouveau jewelers, such as Louis Comfort Tiffany and René Lalique, embraced opal for its luminescent and organic qualities. While October’s birthstone is also the tourmaline, we wanted to highlight the opal for its wide-ranging spectrum of shades, from a matte pink or white, to a fiery red or blue.

E mulating the season’s changing leaves, the hues of November’s birthstone citrine range from burnt sienna to golden amber. A variety of quartz, citrine makes for the perfect autumnal accessory, not to mention it is thought to harness the power and energy of the sun.

O ne of the world’s oldest gems, December’s birthstone, turquoise, plays an important role in ancient and modern culture. Treasured by groups ranging from the Egyptians to the Native Americans, turquoise is thought to be a source of healing. Whether you’re interested in turquoise for its protective properties or simply its rich blue color, there are plenty of beautiful pieces to marvel at in Sotheby’s jewels sales.

A lthough mined in a myriad of colors, garnet is believed to be named for its often deep red hue, reminiscent of a pomegranate seed, or “granatum” in Greek. As the ancient myth goes, Hades lured the innocent and majestic Persephone into the Underworld by giving her pomegranate seeds, and her absence from Earth was thought to have caused winter. The garnet jewels in Sotheby's past and present sales are as tempting and illustrious as the fruit that inspired the gem’s name.

A violet variety of quartz, amethyst is particularly multifaceted. Because of their radiant color, ranging from lavender to royal purple, amethysts were associated with wine in Greek legends and were prominently featured in religious and noble jewels. Until the 19th-century discovery of large Brazilian deposits, amethysts were as valuable as rubies, emeralds and sapphires. The romantic gem was supposedly worn by Saint Valentine himself.

A t times eclipsed by April’s beloved diamond, aquamarine is not to be overlooked. A superb gem in its own right, aquamarine is virtually flawless by nature and few stones can compete with its transparency. Given its calming, bluish-green color, it has long been associated with the sea, and sailors would even use it as a talisman for a prosperous journey. To flow balance and clarity into your life, consider investing in some aquamarine jewels.