Mother Earth’s most amazing treasures

Beneath the Earth's crust, a unique blend of elements, heat, and pressure gives rise to extraordinary gemstones, some of which possess awe-inspiring visual properties. These rare gems, exhibiting phenomena like asterism, play-of-color, and chatoyancy, captivate the imagination and defy logical explanation.

Originating from fortuitous geological conditions, these gems undergo a remarkable journey—from discovery by fortunate miners to expert cutting and faceting, and finally to artful setting by visionary designers. Join us as we uncover the mystery of these natural wonders, gemstones that exhibit phenomena, which ultimately find their place in the collections of the most discerning connoisseurs.

Jewel Metamorphosis: Color-Changing Gemstones

Kaleidoscope digital art by Mariagat. Source.
What’s in a word?
photochromic [ foh-tuh-kroh-mik ] adjective — capable of darkening or changing color when exposed to light
Nature is filled with anomalies that cause spectacular visual effects. The chameleon, for example, changes from dark to pale hues or muted to bright colors to camouflage itself and regulate its body temperature. While color-change gemstones, with their sparkling brilliance, would be impossible to camouflage, their changing color is similarly a reaction to temperature change as a result of light conditions.
Only a very small number of gemstones display the color-change optical phenomena. The result of shifting wavelengths, the technical term for this metamorphosis is photochromism. Elusive and mesmerizing, gems that display this remarkable property include alexandrites, some extremely rare sapphires and chameleon diamonds.

Alexandrites:

Color-Change Russian Alexandrite Ring, 4.12 Carats. M.S. Rau.
In 1834, deep in the Ural Mountains of Russia, one of Earth’s most incredible natural wonders was uncovered. The dramatic color-changing stone was considered such a unique and exquisite specimen that the young Czar Alexander II lent his name to the magnificent gem. Called the alexandrite in his honor, the jewel displays stunningly vivid hues that vary from deep bluish-green, rich purple, and even red and green — the national military colors of Imperial Russia.
It is no wonder that the gem inspired such lore and excitement when uncovered, as it likely was received as a sign from the earth and heavens in support of the Russian Imperial project.
Whitney Alexandrite at the Smithsonian. Source.
While the gem was first discovered in Russia, many of the finest examples have been found in Brazil. Unlike their Russian counterparts that change from green to red, alexandrites that hail from the mines of Brazil display a bluish-green hue under white light and change to a rich, deep purple when viewed under incandescent light.
A 17.08-carat stone known as the Whitney alexandrite can be found in the Smithsonian Museum of Natural History, gifted to the National Gem Collection by Carolyn Wright Whitney. The Whitney alexandrite changes from bluish-green in daylight and fluorescent light to an intense purple in incandescent light. A fantastic rarity, the color change exhibited in alexandrites continues to mystify and delight all who encounter these gems.

Color-Change Sapphire:

Color-Change Sapphire Ring, 12.40 Carats. M.S. Rau.
Sapphires, with their rainbow of hues, have inspired fanfare and legend from the moment of their discovery. The rarest of these gems, however, is the color-changing sapphire. The most prevalent type of color change sapphires are ones that display a deep blue hue in fluorescent light and a beautiful purple color in incandescent light. With their exciting changing colorways, owning color-change sapphires is like having two gems in one.
Sapphire color change is the result of the presence of different metals, such as chromium and vanadium, within the stone. Sapphires can only absorb certain wavelengths of light. In sapphires containing these various metal elements, the type of light source can change the gem’s spectral output, resulting in changing color.

Chameleon Diamonds:

Chameleon Diamond Necklace, 4.41 Carats. M.S. Rau.
What’s in a word? thermochromism [ thərmə-krō-mizəm ] noun — the phenomenon of reversible change of color of a substance with change of temperature
Fancy colored diamonds have captured the fascination of the jewelry industry, commanding the highest prices for their beauty, rarity and unique hues. As demand for these natural wonders increases at an exponential rate, only a handful of gem-quality stones are mined and brought to market every year. While all fancy colored diamonds are distinguished for their colorful splendor and radiance, chameleon diamonds are the only natural colored diamonds with the ability to change color.
A captivating mystery, there is no certain scientific reason for this phenomenon, but it is believed to be due, in part, to the reaction between the diamond's hydrogen and isolated nitrogen atoms interacting when "excited" by increased temperatures and changes in UV light rays. This fascinating process cannot be duplicated, and there exists no known treatment to cause the chameleon effect in other stones. Chameleon diamonds are a true natural wonder.
Chameleon Diamond Ring, 1.29 Carats. M.S. Rau.
Under normal conditions, the color of chameleon diamonds varies from grayish yellowish green to grayish greenish yellow. When heated or exposed to light after prolonged storage in the dark, however, a remarkable color change occurs in real time! The chameleon diamond can temporarily turn an intense brandy or orangy yellow to yellow color.
In some cases, exposure to an ultraviolet lamp for just 60 seconds can cause a chameleon diamond’s color to transform for over 15 minutes, and some even radiate with a phosphorescent yellow glow for up to an hour after light exposure!
Chameleon diamonds are scarce and incredibly sought-after prized possessions, with some even once owned by important leaders like Pedro II, the 19th-century Emperor of Brazil. In fact, part of the reason the chameleon diamond’s metamorphosis remains a scientific mystery is because the specimens are so rarely found, and their value makes it challenging for researchers to procure them.

Lightening Strikes: Opals, Where the Sky Meets the Earth

Some gemologists consider high-quality opals to be rarer than diamonds. Since the 1st century CE, the opal’s dynamic display of various shades captivated all those who beheld their wondrous beauty, including the prolific philosopher Pliny the Elder. By modern accounts, the opal’s magnificent kaleidoscope of hues is now described in the gemological world as play-of-color.
Opals are composed of tiny silica spheres, formed when silica-rich water seeps into deep cracks and voids in the Earth's crust. These spheres diffract light, splitting it into a spectrum of colors and creating interference that allows certain colors to dominate depending on the angle the opal is viewed. The result is a magical display of this beautiful play-of-color phenomenon.
Black Opal and Diamond Ring, 9.10 Carat. M.S. Rau.
Often described as “Lightning Trapped” opal gemstones capture the moment where the sky meets the land as they are the result of nutrient rich precipitation dripping down into the Earth’s crust. Water accounts for an average of 10% of an opal’s weight, though it can reach to 20%. Over millions of years, water from seasonal rains in dry regions such as the Australian Outback dissolves chemical ingredients in desert sand, carrying silica down into the cracks of underground rock. When these silica deposits harden, an opal gemstone is formed.

Chocolate Opals

This extraordinary Mezezo opal specimen hails from the highlands of Africa and exhibits a fantastic play-of-color. Found in the Amhara Province of Ethiopia, this opal weighs an astonishing 791.61 carats. Comprised of a smooth exposed surface attached to a rough nodule, this specimen demonstrates the miraculous thrill of uncovering these gemstones in their natural form.
Ethiopian Mezezo Chocolate Opal Specimen. M.S. Rau.
The opals from this region display a characteristic brown coloring, earning them the the delightful moniker “Chocolate opals.” The gemstone’s warm background creates a dramatic juxtaposition with the opal’s rainbow of bright and colorful refractions. Neon reds and pinks erupt from the opal with glimmers of green and yellow and flickers of indigo and purple making appearances too.
Once used by early peoples as tools, Ethiopian opals only started being formally mined in the 1990s. Usually found in a round nodular form within a three meter thick layer of welded volcanic ash, these opals are plentiful, yet only about 1% of these nodules contain any color at all, let along the striking diversity of color that this rare chocolate opal exhibits.

Opal Varieties:

Opals emerge from the Earth in dozens of varieties and nearly every color of the rainbow. While these gems can be transparent, translucent or opaque, they each display a remarkable play-of-color or an astonishing bold hue.
Some of the most coveted types of opals include the white opal that carries a translucent to opaque milky white or light gray base with a gorgeous rainbow-hued play-of-color. The beauty of the white opal is especially pronounced when they are cut into beads — a rare and highly-desirable occurrence in jewelry design. Ethiopian opals are a relatively new discovery in modern gemology. While “Chocolate opal” specimens from Mezzo were discovered in the 1990s, precious white and crystal Ethiopian opals were only uncovered in the province of Wollo in 2008.
Fire opals are quite unique compared to their cousins. Rather than showing play-of-color against an opaque base, fire opals are coveted for their desirable translucence and fiery red, orange or yellow hues. This special phenomenon is due to the presence of iron during their formation. The best examples of fire opals are found in the state of Querétaro, Mexico.
The black opal is the rarest of all opals, renowned for their unique and stunning beauty. The most exceptional of all black opals hail from the famous Lightning Ridge mine in Australia. Black opals showcase magnificent vibrancy and gleam with striking visual effect, embodying the opal’s appellation as “Lightning Trapped.”
White opal:
Graduated Opal Necklace, 554.00 Carats. M.S. Rau.
Twenty-nine solid opal beads totaling an extraordinary 554.00 carats comprise this mesmerizing necklace. The graduated gems are an impressive size, measuring from 23.8mm to 13mm, with each exhibiting a high level of translucence and a rainbow of colors. Opals are not cut into beads very often, as they are usually found in thin layers, and bigger deposits are extremely rare. To find 29 matching beads of this giant size and exceptional quality is impressive beyond compare.
Ethiopian Opals:
Ethiopian Opal Bead Necklace, 680.00 Carats. M.S. Rau.
Thirty-four solid opal beads totaling approximately 680.00 carats line the length of this eye-catching necklace. The graduated gems are an impressive size and perfectly matched, with each exhibiting a high level of translucence and a rainbow of colors. The gems are set with emerald beads totaling approximately 28.00 carats and black onyx roundels.
Mexican Fire Opals:
Fire Opal Ring By Oscar Heyman, 7.79 Carats. M.S. Rau.
The incredible 7.79-carat cabochon gem is certified by the Deutsche Stiftung Edelsteinforschung (DSEF) German Gem Lab. While Mexican fire opals each burn with a fiery orange glow, most lack the play-of-color seen in other opal varieties. This unique and highly rare Mexican fire opal displays a magnificent play of color, showcasing flashes of gold and yellow. The exquisite gem is accented by two VS2 clarity round diamonds totaling 1.16 carats and set in 18K yellow gold and platinum.

Lasso the Moon: The Lunar Allure of Moonstones

Moonstone Bracelet by Raymond Yard, 65.02 Carats. M.S. Rau.
What’s in a word? adularescence [ aj-uh-luh-res-uhnt ] adjective — the changing milky bluish iridescence originating from below the surface of a stone, that occurs when light is reflected between layers of minerals.
As the playful name suggests, the moonstone conjures the same lunar appeal as its counterpart in the sky. Moonstone is a gem-quality variety of feldspar known for its pearl-like, iridescent luster. Known scientifically as adularescence, this phenomena present in feldspar produces a dramatic visual illusion. When one examines moonstone, a billowy soft blue or sometimes milky white light appears to move across the gemstone. This effect is most observable to the eye when the gem is cut in a cabochon — a spherical, unfaceted cut. With their dramatic rounded shape, pale blue hue and mild white mirage, these gems really do mirror the Earth’s moon.
Moonstone And Diamond Necklace By Henry Dunay. M.S. Rau.
With varying degrees of luminosity and a plethora of beautiful colors, these gems have captivated gem-lovers and top jewel designers over the decades.

Gazing at the Stars: Star Sapphires & Rubies

What’s in a word? asterism [ as-tuh-riz-uhm ] noun —a property of some crystallized minerals of showing a starlike luminous figure in transmitted light or, in a cabochon-cut stone, by reflected light.
Of all the various gem phenomena present, this effect certainly appears to be endowed by the heavens. Called asterism in scientific circles, jewelers have long coveted the mysterious sapphires and rubies that display what they call “stars.” These celestial beauties feature a four- or six-rayed star pattern of light.

These stars are caused by fibrous inclusions. Tiny needle-like titanium dioxide, or rutile, fibers form within the gemstone, creating what appears to be the rays of a star when viewed under a single, concentrated light source. Like the lunar effect of the moonstone, these stunning constellation-makers appear best in cabochon cuts.

Star Sapphire Cabochon Ring, 12.39 Carats. M.S. Rau.

Sapphires are not the only prized gem to display the rare star phenomena. Radiant red rubies can also exhibit asterism. Most star rubies are found in Burma — the site of the coveted pigeon’s blood hue rubies. Star rubies occur frequently in this region due to the uniform, tightly knit formation of silk in these gemstones.

Art Deco Star Ruby Bracelet By Cartier, 15.00 Carats. M.S. Rau.

Star sapphires and rubies glow with an internal galaxy, harnessing the stars of the sky within the bounds of their form. When it comes to this phenomenon, no two stars are the same. The star’s points or arms can vary from thick to thin and may even vary in length. The way the effect moves across the surface of a star gem varies too, with some appearing to travel smoothly across the gem and others appearing to jump out when viewed from a different angle. With their individualized appearance and movement, no two star sapphires or rubies are exactly alike, making them all the rarer and more mystifying.

Feline Phenom: Cat’s Eye

Cat’s Eye Chrysoberyl and Baguette Diamond Ring. M.S. Rau.
What’s in a word? chatoyant [ shuh-toi-uhnt ] adjective — having a changeable luster or color with an undulating narrow band of white light
These remarkable gems seem to purr with allure. Called Cat's Eye chrysoberyls, these visually arresting jewels, with their winking bands of light, conjure the majesty of the animals for which they are named. Entrancing rarities, Cat's Eye chrysoberyls are found only in a few deposits around the world.
When this dramatic feline effect appears in chrysoberyl stones, it is known as chatoyancy. Caused by the presence of fine, needle-like inclusions or fibers, this dramatic visual effect gives these gems the appearance of a cat's mesmerizing slitted eye. No two Cat's Eyes are the same, and like their Animal Kingdom counterparts, each effect travels across the gem with its own curiously individual movement.
Chrysoberyl is considered a protective gemstone and seen as a particularly effective protective talisman when in its Cat’s Eye form. The gem's signature golden tones are often also associated with wealth, making them a coveted possession of gemstone connoisseurs. With its golden hue and protective eye, Cat's Eye chrysoberyl has long been thought to bring protection and good fortune to wearers. The rare gemstone first gained popularity in the late 1800s when the Duke of Connaught gave it to his betrothed as an engagement token.

Believed to ward off unforeseen danger, Cat's Eye lore also posits that the rare gemstone can help with disorders of the eye, promoting the wearer's mobility and reflexes (cat-like, perhaps!), as well as increasing night vision. Some believe the stone carries spiritual properties and that wearing it can enhance intuition, concentration and even psychic abilities! Regardless of the potency of these effects, the Cat's Eye chrysoberyl's mystifying effect has certainly generated a mythos all its own. The gemstone carries a powerful energy, recalling the majesty of nature's most regal animals.

Men's Cat's Eye Chrysoberyl Ring, 6.00 Carats. M.S. Rau.

Glorious Glow: Paraiba Tourmalines

What’s in a word? bioluminescence [ bahy-oh-loo-muh-nes-uhns ] noun — the biochemical emission of light by living organisms such as fireflies and deep-sea fishes.

With an otherworldly glow, the magnificent Paraiba tourmaline conjures the appearance of another of Mother Earth’s most enrapturing phenomena: the bioluminescent glow of the ocean. With their effulgent, lit from within appearance, the electric blue color of these remarkable gems captivates the eye and the imagination. While other gemstone phenomena like opals have been revered since ancient times, the Paraiba is a relatively new discovery, only first making waves in 1981.

Brazilian Paraiba Ring, 6.06 Carats. M.S. Rau.

In 1981, the gem miner Heitor Dimas Barbosa, commonly known among the local villagers as “Heitor the Fool,” began tunneling into the hill behind São José de Batalha, Paraíba, Brazil. Barbosa was determined that his hunch would lead to finding a new gemstone. Despite having no electricity or dependable water, Barbosa persevered on his quest for more than six years, relentlessly digging through the rugged and arid landscape. In 1987, his efforts were rewarded by the discovery of the first Brazilian Paraiba tourmaline, an electrifying gem unlike any stone ever found before.

Earth’s newest gemological phenomenon, this special tourmaline is most renowned for its signature “Windex hue” and dazzling glow—the result of the presence of copper within the mines. As such, these rare stones have only been found in the copper-rich mines of Brazil, Nigeria and Mozambique.

Untreated Paraiba Tourmaline Ring, 23.24 Carats. M.S. Rau.

Conclusion:

Spectacular and spellbinding, gemstone phenomena enchant all who encounter them. Like stars in the sky, flashes of lightning, or the miraculous color-changing chameleon, these remarkable jewels awaken a sense of wonder in the phenomena of the natural world. These seemingly magical properties further underscore the lore of gemstones. Often thought to carry healing powers or offer protection and good fortune, these gemological phenomena present visual evidence of the power of gemstones.

Though much of this phenomena can be explained by science, the optical wonders of these gemstones still seem to defy logic. Alas, whether the result of a specific set of physical and chemical properties or the power of some enigmatic mystical force, these jewels remain true marvels of nature, inspiring awe and reverence from every angle.
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