December Birthstones | Tanzanite, Zircon & Turquoise
December’s birthstones offer three ways to fight the winter blues: tanzanite, zircon, and turquoise—all of them, appropriately, best known for beautiful shades of blue.
These gemstones range from the oldest on Earth (zircon), to one of the first mined and used in jewelry (turquoise), to one of the most recently discovered (tanzanite).
All of these stones are relatively inexpensive, but their beauty rivals even precious gemstones. Colorless zircon is a convincing replacement for diamond, tanzanite often substitutes sapphire, and turquoise is unmatched in its hue of robin’s egg blue.
Whatever your style preference or budget, one of December’s three birthstones will match your true blue desires.
Tanzanite is the exquisite blue-purple variety of the mineral zoisite that is only found in one part of the world. Named for its limited geographic origin in Tanzania, tanzanite has quickly risen to popularity since its relatively recent discovery.
Zoisite had been around more than a century and a half before this rare blue variety was found in 1967. Trace amounts of vanadium, mixed with extreme heat, cause the blue-purple color—which ranges from pale blue to intense ultramarine with violet undertones.
Due to pleochroism, tanzanite can display different colors when viewed from different angles. Stones must be cut properly to highlight the more attractive blue and violet hues, and deemphasize the undesirable brown tones.
The majority of tanzanite on the market today is heat treated to minimize the brown colors found naturally, and to enhance the blue shades that can rival sapphire.
Tanzanite is still only found on a few square miles of land in Tanzania, near majestic Mount Kilimanjaro. Its price and availability are directly tied to mines in this region, most of which are now slowing production significantly.
Tanzanite measures 6.5 to 7 on the Mohs scale of hardness—which is not nearly as hard as the sapphire it often substitutes. Given its vulnerability to scratch during daily wear and abrasion, tanzanite is better suited for earrings and pendants than rings.
Between its deep blue color and its limited supply, tanzanite is treasured by many—whether one is born in December or not!
Unlike many well-known gemstones that have been in use for centuries, tanzanite’s history is relatively modern.
The common story of tanzanite’s discovery tells of Maasai herders who found blue crystals in the Merelani Hills near Arusha, Tanzania, while tending livestock in 1967. They notified a prospector named Manuel d’Souza, who promptly registered claims with the government to begin mining.
Initially, d’Souza thought he was mining sapphire, but the crystal was soon identified as a vibrant blue variety of zoisite—a mineral that had been around since the early 1800s.
Tiffany & Co. recognized this blue gem’s potential to rival more expensive sapphire and agreed to become its main distributor. Instead of publicizing “blue zoisite” —which sounded a little too much like “suicide” —Tiffany named the gemstone “tanzanite” to highlight its exclusive geographic origin and introduced it with a promotional campaign in 1968.
An estimated two million carats of tanzanite were mined before the Tanzanian government nationalized the mines in 1971. The government divided the mines into four sections, or blocks, in 1990. Tanzanite One Mining Ltd., the world’s largest tanzanite producer, holds the rights to Block C, which is larger than the other blocks combined.
An independent study from 2012 suggests, at a production rate of 2.7 million carats per year, that Block C’s tanzanite deposits may deplete in as soon as 30 years.
Tanzanite may not have the long history of other gemstones, but with such limited supplies and rapidly growing popularity, it is highly prized for its rare beauty.
There are many reasons to buy tanzanite, whether to celebrate a December birthday, to commemorate a 24th wedding anniversary, or simply to enjoy the gemstone’s rare, vibrant blue. It even serves as a less expensive substitute for sapphire.
Most tanzanite on the market today gets its blue color from heat treatment, which minimizes the stone’s natural brown hues. Treated tanzanite has become the norm, so although it’s undetectable, it’s usually assumed.
Generally, tanzanite follows the same value parameters as diamonds. Buying from a reputable American Gem Society jeweler will ensure that you get what you pay for.
Color, of course, is tanzanite’s most prized trait, especially when it’s deeply saturated blue with violet hues. Paler shades are less expensive.
Tanzanite is pleochroic, which means it displays different colors from different angles. So the cut significantly influences the color, which determines the price. Cutting a stone to emphasize the blue may waste more of the rough, but because this color is more valuable than violet, the cutter may choose a small fine-colored blue gemstone over a larger violet one.
Most faceted tanzanite weighs less than five carats. Stones heavier than 50 carats are rare, although The Smithsonian Institution’s collection includes a faceted 122.7-carat tanzanite. The world’s largest rough tanzanite weighed 16,839 carats.
Because tanzanite is only found within a few square miles in Tanzania, its price and availability can fluctuate sharply, depending what happens there.
Although it doesn’t have a long history of admiration like some gemstones, tanzanite didn’t take long to rise through the ranks. Between its exclusive origin, finite supply, and intense blue beauty, tanzanite continues to grow in popularity.
Zircon is an underrated gemstone that’s often confused with synthetic cubic zirconia due to similar names and shared use as diamond simulants. Few people realize that zircon is a spectacular natural gemstone available in a variety of colors.
The name “zircon” likely comes from the Persian word zargun, meaning “gold-colored.” Others trace it to the Arabic zarkun, meaning “vermillion.” Given its wide range of colors—spanning red, orange, yellow, green, blue, and brown—both origins are plausible.
Zircon commonly occurs brownish red, which can be popular for its earth tones. However, most gem-quality stones are heat treated until colorless, gold or blue (the most popular color). Blue zircon, in particular, is the alternative birthstone for December.
Color differences in zircon are caused by impurities, some of which (like uranium) can be slightly radioactive. These gemstones are also treated with heat to stabilize the radioactivity.
While radiation can break down zircon’s crystal structure, it plays a crucial role in radiometric dating. Zircon, the oldest mineral on Earth, contains important clues about the formation of our planet.
Colorless zircon, known as Matura Diamond, displays brilliance and flashes of multicolored “fire” that can rival fine diamond. There’s one key difference though: Zircon is more brittle. Though it measures 7.5 on the Mohs scale of hardness, its faceted edges can chip.
Zircon from Australia dates back 4.4 billion years. Australia still leads the world in zircon mining, producing 37 percent of the world’s supply. Other sources include Thailand, Sri Lanka, Tanzania, Cambodia, Canada, and the United States.
Since the Middle Ages, people have believed that zircon can induce sleep, ward off evil, and promote prosperity.
Zircon is the oldest mineral on Earth, dating back more than 4.4 billion years. Found in the Earth’s crust, it’s common in most sands and sedimentary deposits, as well as metamorphic rocks and crystallized magma.
Due to its chemical makeup, zircon has survived ages of geologic events like erosion and pressure shifts—recording these changes like a time capsule. Zircon contains the radioactive element uranium, which changes the gemstone’s chemical structure and color over time, giving us important clues about the formation of our planet.
During the Middle Ages, people believed that zircon could induce sound sleep, ward off evil, and bring prosperity and wisdom.
Blue zircon, in particular, was popular during Victorian times, and frequently adorned English estate jewelry from the 1880s. Zircon with a cloudy or smoky appearance was also popular in mourning jewelry.
In the 1920s, heat treatment became customary practice to enhance the color of zircon gemstones for jewelry. Zircon has also been used in the decorative ceramics industry.
While zircon is a popular gemstone among collectors for its range of colors, consumers seem most enamored with the blue variety, and otherwise confused about the history and possibility of this expansive gemstone.
Zircon is often confused with Cubic Zirconia (CZ). CZ is one of the best-known, man-made simulants and is the crystalline form of zirconium dioxide (ZrO2). Zircon is a naturally-occurring mineral, which is zirconium silicate (ZrSiO4).
Whether you’re buying blue zircon to celebrate a December birthday, or selecting another shade just to own a gorgeous piece of Earth’s oldest history, zircon offers many options. A wide range of colors at relatively low cost make zircon a popular gemstone with collectors.
While zircon generally follows the same value factors as diamonds, it’s best to visit an American Gem Society jeweler who can help you select the right gemstone for you.
Zircon is available in a rainbow of colors. Reddish brown earth tones are common, but bright red or green gemstones have higher market value.
Blue zircon is the most popular variety, comprising 80 percent of all zircon sales and commanding the highest prices. Blue is almost always the result of heat treatment.
Zircon is often cut in the brilliant style to showcase its diamond-like luster and fire. Facets must be cut carefully (to avoid chipping this brittle stone) and properly (to avoid the blur caused by zircon’s strong double refraction).
The size of zircon depends on its color. Blue and green gemstones come in sizes up to 10 carats, orange and yellow up to five. Rare red and purple stones are typically smaller.
Because zircon is one of the heaviest gemstones, it appears smaller than other gemstones of equal carat weight.
Often considered the best-looking natural substitute for diamond, zircon is gaining popularity—not just in colorless form, but across the spectrum. Whether you’re seeking a birthday blue or any other hue, you can find the zircon just right for you.
Admired since ancient times, turquoise is known for its distinct color, which ranges from powdery blue to greenish robin’s egg blue. It’s one of few minerals to lend its name to anything that resembles its striking color.
The word “turquoise” dates back to the 13th century, drawing from the French expression pierretourques, which referenced the “Turkish stone” brought to Europe from Turkey.
Ancient Persia (now Iran) was the traditional source for sky blue turquoise. This color is often called “Persian blue” today, regardless of its origin. The Sinai Peninsula in Egypt was also an important historical source.
The U.S. is now the world’s largest turquoise supplier. Nevada, New Mexico, California, and Colorado have produced turquoise, but Arizona leads in production by value, as well as quality. The stone’s popularity here makes it a staple in Native American jewelry.
Turquoise is found in arid regions where rainwater dissolves copper in the soil, forming colorful nodular deposits when it combines with aluminum and phosphorus. Copper contributes blue hues, while iron and chrome add a hint of green.
Some turquoise contains pieces of host rock, called matrix, which appear as dark webs or patches in the material. This can lower the stone’s value, although the uniform “spiderweb” pattern of Southwestern turquoise is attractive.
Turquoise is sensitive to direct sunlight and solvents like makeup, perfume, and natural oils. The hardest turquoise only measures 6 on the Mohs scale, which made this soft gemstone popular in carved talismans throughout history.
From ancient Egyptians to Persians, Aztecs and Native Americans, kings and warriors alike admired turquoise for thousands of years. It adorned everything from jewelry to ceremonial masks to weapons and bridles—granting power and protection, particularly against falls.
Highly esteemed for its striking namesake color and its ancient history, turquoise remains popular through time.
Cultures around the world have admired the distinct color of turquoise since ancient times.
The earliest evidence comes from ancient Egyptian tombs, which contain elaborate turquoise jewelry dating back to 3000 BCE. Egyptians set turquoise in gold necklaces and rings, used it as inlay and carved it into scarabs. Most notably, King Tut’s iconic burial mask was extravagantly adorned with turquoise.
The oldest turquoise mines are located in the Sinai Peninsula of Egypt. One sat near an ancient temple dedicated to Hathor, the Greek goddess of love and joy—worshipped as a protector in the desert and as the patron saint of mining. Egyptians called turquoise mefkat, which meant “joy” and “delight.”
Ancient Persians decorated extensively with turquoise, often engraving it with Arabic script. Turquoise covered palace domes because its sky blue color represented heaven. (This later inspired the use of turquoise in buildings like the Taj Mahal.)
Believing turquoise guaranteed protection, Persians adorned their daggers and horses’ bridles with it. Their name for turquoise, pirouzeh, meant “victory.”
Persians wore turquoise jewelry around their necks and in their turbans. They believed it offered protection by changing color to warn of pending doom. (Turquoise can, in fact, fade if exposed to sunlight or solvents.)
When Turkish traders introduced this “Persian blue” stone to Europe via the Silk Road in the 13th century, they influenced the gemstone’s name. The word “turquoise” comes from the French pierre tourques for “Turkish stone.”
Meanwhile, pre-Columbian Native Americans mined the turquoise gemstone throughout the present-day southwestern United States. Shamans used it in sacred ceremonies to commune with the spirit of the sky.
Apache Indians believed that attaching turquoise to bows (and later, firearms) improved a hunter’s accuracy.
Turquoise became valuable in Native American trade, which carried North American material toward South America. Consequently, Aztecs cherished turquoise for its protective power, and used it on ceremonial masks, knives, and shields.
The turquoise-studded silver jewelry that’s commonly associated with Native Americans today originated in the 1880s, when a white trader convinced a Navajo craftsman to transform a silver coin into turquoise jewelry.
While many historic turquoise deposits have depleted over the gemstone’s long lifetime, some small mine operations (mainly in the U.S.) still produce fine material today.
Turquoise, the traditional birthstone of December, is also gifted on the 11th wedding anniversary. But buying turquoise doesn’t require special occasions; its namesake blue color has been internationally revered for centuries as a symbol of protection, friendship, and happiness.
Thanks to its historical and cultural significance in many Native American tribes, turquoise remains most popular throughout the southwestern U.S.—which supplies most of the world’s turquoise today.
Turquoise is one of few gemstones not judged by the 4Cs of diamond quality. Instead, the main factors that determine its value are color, matrix, hardness, and size.
The most prized turquoise color is a bright, even sky blue. Greenish tones can lower the value of a stone, although some designers prefer it.
Some turquoise—particularly the material mined in the American Southwest—contains remnants of its host rock, known as matrix. These splotches decrease a gemstone’s value. Although it can create an attractive “spider web” pattern, unblemished varieties command higher prices.
The porosity, texture, and hardness of turquoise varies greatly. Fine-colored turquoise that’s too soft or chalky will lose color—and value. Course, porous material is usually treated to make it stronger, smoother, and shinier.
Because of its fragility, turquoise is often treated to enhance durability and color. Some treatments involving wax and oil are relatively harmless, while other methods—including dye, impregnation, and reconstitution—are more controversial. Seek out an American Gem Society jeweler who can help you find the best quality turquoise.
Like other opaque gemstones, turquoise is commonly priced by size, rather than weight. It’s available in a variety of sizes, but color is always the determining factor.
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