The final month of the Gregorian calendar, December, is associated with a unique and vibrant trio of birthstones: turquoise, zircon, and tanzanite. Unlike months with a single traditional gem, December offers a palette of colors ranging from the sky-blue of turquoise to the fiery brilliance of zircon and the deep violet-blue of tanzanite. These stones are not merely decorative; they are steeped in history, geological wonder, and cultural significance. As symbols of good fortune, success, and protection, December's birthstones have been cherished across millennia, from ancient civilizations to modern jewelry connoisseurs. This article delves into the rich history, geological origins, gemological properties, and symbolic meanings of these three distinct gems, providing a thorough exploration for enthusiasts, buyers, and students of gemology.
History and Lore
The tradition of birthstones is deeply rooted in antiquity, with origins tracing back to the Breastplate of Aaron, as described in the Old Testament, which featured twelve gemstones representing the twelve tribes of Israel. Over centuries, this biblical association evolved, and by the 18th century, a more formalized list of birthstones began to take shape in Poland, linking specific gems to calendar months. The modern list, largely standardized by the National Association of Jewelers in 1912 and updated by the American Gem Society, solidified December's association with turquoise, with zircon and tanzanite later added as alternatives to accommodate the stone's varying availability and the desire for more contemporary options.
Turquoise is arguably the most ancient of the three, with a history that spans continents and cultures. Its name derives from the French pierre turquoise, meaning "Turkish stone," as the gem was first brought to Europe from the mines of Persia (modern-day Iran) via Turkey. However, its use predates this trade route by millennia. Archaeological evidence shows that turquoise was mined and worn in ancient Egypt, where it was used to create intricate jewelry, amulets, and burial ornaments for pharaohs. The Egyptians believed the stone was a symbol of rebirth and protection, often associating its color with the heavens. Similarly, in ancient Persia, turquoise was a talisman against unnatural death and was believed to ensure the wearer's safety. Native American cultures, particularly the Navajo, Zuni, and Hopi peoples of the Southwestern United States, have a profound connection with turquoise, using it in sacred ceremonies and as a material for exquisite silverwork. For these cultures, the stone represents the sky, water, and spiritual protection.
Zircon, the second December birthstone, has a history that is both illustrious and often misunderstood due to its visual similarity to higher-value gemstones. The name "zircon" may come from the Persian word zargun, meaning "gold-colored," though the stone is most prized for its fiery brilliance and range of colors, including blue, yellow, green, brown, and red. For centuries, zircon was confused with diamond and other gemstones. In the Middle Ages, it was believed to aid in sleep, promote prosperity, and guard against evil spirits. It was also thought to bring honor and wisdom to its wearer. The most famous historical association is with the "Mogok" zircon from Myanmar (Burma), which was highly valued for its exceptional clarity and fire. However, the stone's reputation was somewhat tarnished in the 20th century when it became a popular, inexpensive diamond simulant, leading to public confusion. Despite this, natural zircon remains a gem of significant value and historical importance.
Tanzanite is the newest addition to the December birthstone family. Its history is remarkably short, beginning in 1967 when the gem was discovered in the Merelani Hills of Tanzania, near the base of Mount Kilimanjaro. The gem was initially marketed by the Tiffany & Co. jewelry company, which recognized its unique color and rarity. Named after its country of origin, tanzanite quickly gained popularity as a modern alternative to sapphire and amethyst. Its discovery is a geological rarity, as it is believed that tanzanite exists in only one place on Earth, making it exponentially rarer than diamond. While it lacks the ancient lore of turquoise or zircon, tanzanite's story is one of modern gemology and marketing success, capturing the imagination of a new generation of jewelry buyers.
Geological Formation and Sources
The formation and sourcing of these three gems are as diverse as their appearances. Each originates from distinct geological processes and is mined in specific, often limited, regions of the world.
Turquoise is a hydrous phosphate of copper and aluminum. It forms in arid regions where acidic, copper-rich groundwater seeps through and reacts with minerals containing aluminum and phosphorus. This process occurs over millions of years, creating nodules or veins in host rocks. The most significant sources of turquoise include: - Iran (Persia): Historically the most prized source, producing the classic "sky-blue" turquoise with a fine, even color and minimal matrix (the host rock). The Nishapur region is particularly famous. - United States: The Southwestern states—especially Arizona, New Mexico, and Nevada—are major producers. American turquoise varies widely in color and matrix, from the bright blue of the Sleeping Beauty mine to the greenish-blue with black spiderweb matrix from the Kingman mine. - China: A major contemporary source, producing large quantities of turquoise in various grades. - Egypt: The Sinai Peninsula was an ancient source, though production has declined. - Mexico: Known for its "royston" turquoise, which often features a distinctive blue-green color.
Zircon is a zirconium silicate (ZrSiO₄) and is one of the oldest minerals on Earth, with some crystals dating back over 4.4 billion years. It forms in igneous and metamorphic rocks. The gem-quality zircon used in jewelry is primarily sourced from: - Cambodia: Known for producing high-quality, heat-treated blue zircon. - Sri Lanka: A traditional source for zircon in a variety of colors, including the popular blue. - Myanmar (Burma): Historically famous for its "Mogok" zircon, prized for its clarity and fire. - Australia: The main source for brownish zircon, which is often heat-treated to produce blue. - Brazil, Norway, and Nigeria: Also produce gem-quality zircon.
Tanzanite is the blue-violet variety of the mineral zoisite (Ca₂Al₃(SiO₄)₃(OH)). It is formed by the metamorphism of aluminous rocks, a process that requires specific geological conditions. The Merelani Hills in Tanzania are the only known commercial source of tanzanite. The mining area is extremely localized, covering just a few square kilometers. The gem is often found in association with other minerals like graphite and diopside. Due to its single-source origin, tanzanite is considered at least 1,000 times rarer than diamond. Mining is challenging, and the supply is finite, which contributes to its high value and status.
Gemological Properties
Understanding the physical and optical properties of these gems is essential for identification, valuation, and care. The following table summarizes key gemological data for turquoise, zircon, and tanzanite.
| Property | Turquoise | Zircon | Tanzanite |
|---|---|---|---|
| Chemical Formula | CuAl₆(PO₄)₄(OH)₈·4H₂O | ZrSiO₄ | Ca₂Al₃(SiO₄)₃(OH) |
| Crystal System | Triclinic | Tetragonal | Orthorhombic |
| Hardness (Mohs) | 5 - 6 | 6.5 - 7.5 | 6.5 - 7 |
| Specific Gravity | 2.6 - 2.9 | 4.6 - 4.7 | 3.35 |
| Refractive Index | 1.61 - 1.65 | 1.92 - 2.01 | 1.69 - 1.70 |
| Luster | Waxy to subvitreous | Adamantine to vitreous | Vitreous to adamantine |
| Common Treatments | Waxing, impregnation, stabilization | Heat treatment (to improve color) | Heat treatment (to enhance color) |
| Durability | Porous, prone to cracking and discoloration. Not suitable for daily wear rings. | Good durability, but can be brittle due to cleavage. | Fair to good, but can be sensitive to blows and rapid temperature changes. |
Turquoise is a relatively soft and porous gem. Its hardness (5-6 on the Mohs scale) makes it susceptible to scratches and abrasion. Its porous nature means it can absorb oils, chemicals, and perspiration, leading to discoloration. To enhance stability and color, most commercial turquoise is treated with wax, oil, or impregnated with a resin (stabilized turquoise). The quality of turquoise is often judged by its color (even, medium to medium-light blue is most valued) and the amount and pattern of the host rock matrix.
Zircon is one of the hardest natural gemstones, with a hardness of 6.5 to 7.5, making it durable enough for most jewelry, including rings. However, it has perfect cleavage in two directions, meaning it can be split with a sharp blow, requiring careful cutting and setting. Zircon's high refractive index (1.92-2.01) gives it exceptional brilliance and fire, often exceeding that of diamond. The most common color for jewelry is blue, which is typically produced by heating brown zircon. Heat treatment is standard and permanent for zircon.
Tanzanite has a hardness of 6.5 to 7, making it suitable for jewelry but less durable than sapphire or diamond. It is important to note that tanzanite has poor toughness due to its cleavage and is sensitive to rapid temperature changes, which can cause fracture. Most tanzanite on the market has been heat-treated to achieve its vivid blue-violet color; untreated tanzanite is typically brownish. The gem exhibits strong trichroism, showing blue, violet, and reddish tones depending on the crystal orientation, which is a key identifier.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, each of December's birthstones carries a rich tapestry of symbolic meanings and metaphysical beliefs, many of which have persisted from ancient times to the present.
Turquoise is universally regarded as a stone of protection, healing, and good fortune. In many cultures, it is believed to ward off negative energy and evil spirits. It is often called a "master healer" stone, thought to support the immune system, soothe inflammation, and aid in tissue regeneration. Emotionally, turquoise is associated with balance, inner calm, and creative expression. It is the traditional anniversary gemstone for the 11th year of marriage.
Zircon is historically linked to prosperity, honor, and wisdom. It is believed to bring spiritual growth and clarity of mind. Some traditions hold that zircon aids in sleep, promotes prosperity, and guards against evil. Blue zircon, in particular, is associated with peace and tranquility. It is also the anniversary gemstone for the 4th year of marriage.
Tanzanite, as a modern gem, has developed its own set of metaphysical associations. It is often called the "stone of transformation," believed to facilitate a higher consciousness, intuition, and spiritual awakening. It is said to promote a sense of calm and peace, helping to alleviate stress and anxiety. Some believe tanzanite can open the throat chakra, aiding in clear communication and self-expression.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these birthstones, given their differing physical properties.
Turquoise requires gentle handling. It should be cleaned with a soft, damp cloth and mild soap, avoiding harsh chemicals, ultrasonic cleaners, and steam. It is best stored separately from other jewelry to prevent scratching. Due to its porosity, it is not recommended for daily wear in rings or bracelets, as it is prone to damage from impacts and exposure to lotions, perfumes, and perspiration.
Zircon, while harder, should be cleaned with warm water, mild detergent, and a soft brush. Avoid sudden temperature changes and ultrasonic cleaners, as the stone's cleavage can be exploited. It is durable enough for most jewelry but should be protected from sharp blows.
Tanzanite is the most delicate of the three in terms of care. It should never be cleaned in an ultrasonic cleaner or with steam, as this can cause fracture. Cleaning should be done with a soft brush and mild soapy water, followed by gentle drying. It is crucial to protect tanzanite jewelry from knocks and rapid temperature changes. When setting tanzanite in rings, protective settings like bezels are recommended.
Conclusion
The birthstones of December—turquoise, zircon, and tanzanite—offer a remarkable study in diversity. From the ancient, protective talisman of turquoise to the fiery, brilliant zircon and the modern, transformative tanzanite, each gem tells a unique story of geological creation, cultural significance, and enduring beauty. Together, they form a triad that captures the essence of the winter month: the serene sky-blue of turquoise reflects the clear winter skies, the sparkle of zircon mimics the festive lights of the season, and the deep violet-blue of tanzanite evokes the twilight of the year's end. For those born in December, these stones are more than mere adornments; they are connections to a deep history, a testament to the Earth's artistry, and symbols of good fortune, protection, and spiritual insight. As the gemological world continues to appreciate these stones, their legacy as December's birthstones remains firmly established, cherished for their unique qualities and the stories they carry.