The month of December is uniquely associated with three distinct birthstones: Tanzanite, Zircon, and Turquoise. This multiplicity offers those born in the final month of the year a diverse palette of colors, ranging from the deep violet-blue of Tanzanite to the brilliant ice-like fire of Zircon and the iconic sky-blue of Turquoise. While Turquoise has ancient roots, Tanzanite and Zircon represent the modern spectrum of December’s gems, each possessing unique geological origins, gemological characteristics, and symbolic meanings.
Tanzanite, a relative newcomer to the gemological world, has rapidly ascended to become a dominant force in the jewelry market due to its singular color and compelling backstory. Blue Zircon, often confused with the synthetic cubic zirconia, is a natural gemstone with a high refractive index that rivals the sparkle of diamonds. Together, these stones provide a contemporary alternative to the traditional turquoise, catering to modern tastes while maintaining the deep-seated human tradition of wearing birthstones.
This article explores the specific attributes of Tanzanite and Blue Zircon, examining their geological formation, physical properties, and the commercial landscape that defines their availability, particularly in the context of jewelry designed for children and infants.
The December Birthstone Trio: An Overview
The modern birthstone list, established by the National Association of Jewelers (NAJ) in 1912 and subsequently updated, designates Tanzanite, Zircon, and Turquoise as the birthstones for December. This list provides a framework for jewelers and consumers, but the specific choice often depends on personal preference for color and durability.
Tanzanite is the most modern addition, officially added to the list in 2002. It is prized for its trichroic nature, displaying shades of blue, violet, and burgundy depending on the viewing angle. Blue Zircon, conversely, is one of the traditional December stones, historically valued for its brilliance and clarity. It is important to distinguish natural Zircon from cubic zirconia (CZ), a synthetic diamond simulant; natural Zircon is a silicate mineral with its own distinct properties and geological history.
The commercial appeal of these stones is evident in the variety of jewelry available, ranging from high-end custom pieces to accessible children’s jewelry. In the current market, consumers often seek these stones not only for their aesthetic beauty but also for the safety and comfort features associated with modern jewelry designs, such as screw-back mechanisms for children.
Tanzanite: The Gem of a Single Source
Tanzanite is one of the most significant gemological discoveries of the 20th century. Its story is inextricably linked to a specific geographic location, making it a "single-source" gemstone.
Geological Formation and Discovery
Tanzanite is the blue-to-violet variety of the mineral zoisite. It is found exclusively in the Merelani Hills of Northern Tanzania, near the base of Mount Kilimanjaro. The gem was formed millions of years ago through a unique geological process involving the heating of zoisite by magma intrusions, which later cooled to form the present-day deposits.
The stone was first discovered in significant quantities in the late 1960s. Its rapid rise to prominence was fueled by the gemstone giant Tiffany & Co., which recognized its potential and launched a major marketing campaign in 1968, naming the gem "Tanzanite" after its country of origin. This strategic branding helped distinguish it from other blue gemstones like Sapphire and Iolite.
Gemological Properties
Tanzanite is cherished for its intense color, which is often enhanced through a controlled heating process. The unheated rough material often exhibits a brownish hue, which is removed by heating to temperatures between 350°C and 400°C, revealing the stable blue-violet color.
- Hardness: On the Mohs scale of hardness, Tanzanite ranks between 6 and 7. This makes it a somewhat softer gemstone compared to Sapphire (Mohs 9) or Diamond (Mohs 10). Consequently, while it is suitable for earrings and pendants, it requires more care when set in rings due to its susceptibility to scratches and abrasions.
- Color: The most prized color is a deep, saturated violet-blue. The gem exhibits strong pleochroism, appearing blue in one direction, violet in another, and reddish-burgundy in a third.
- Clarity: High-quality Tanzanite is typically eye-clean, meaning it lacks visible inclusions to the naked eye.
Symbolism and Lore
Due to its recent discovery, Tanzanite lacks the ancient lore associated with gems like Turquoise or Zircon. However, modern metaphysical beliefs have quickly attached meaning to it. It is often associated with transformation and spiritual awakening. Some believe the stone possesses a high vibrational energy that promotes intuition and communication. It is frequently marketed as a stone of "vision" and "clarity," intended to help the wearer navigate change.
Blue Zircon: The Diamond Alternative
Blue Zircon is the oldest of the December stones in terms of human history, yet it is frequently misunderstood due to its name.
Distinction from Cubic Zirconia
A critical distinction must be made between Zircon and cubic zirconia (CZ). * Zircon is a natural mineral (zirconium silicate, ZrSiO₄). It is a legitimate gemstone with a long geological history. * Cubic Zirconia is a synthetic material created in laboratories to simulate diamonds. It has no chemical or physical relationship to natural Zircon.
The confusion in the marketplace is evident in product descriptions for children's jewelry, where synthetic stones are often marketed to resemble the birthstone. For example, some jewelry listings for December birthstone earrings for children utilize cubic zirconia or Swarovski crystals to mimic the look of Tanzanite or Blue Zircon. While these synthetic alternatives offer sparkle and affordability, they differ chemically and physically from the natural gemstones.
Properties and Durability
Natural Blue Zircon is renowned for its brilliance. It possesses a high refractive index (1.92–1.98), which is higher than that of a sapphire, giving it a diamond-like fire. However, it is doubly refractive, meaning it can display doubling of facets when viewed through the gem.
- Hardness: Zircon ranks at 6 to 7.5 on the Mohs scale. However, it is known for being brittle and susceptible to chipping due to its cleavage properties. This makes it a challenging stone to set and wear in rings unless protected by a bezel setting.
- Color: While Zircon occurs in a variety of colors (red, yellow, brown, green), the blue variety is the most popular for December. The blue color is typically achieved through heat treatment of brownish zircon crystals.
Historical Significance
Zircon is one of the oldest minerals on Earth, with deposits dating back billions of years. Throughout history, it has been regarded as a protective stone. In the Middle Ages, it was believed to aid in sleep, bring prosperity, and ward off evil spirits. It was also used as a talisman for travelers.
The Market for Children's Birthstone Jewelry
A significant portion of the provided materials focuses on jewelry designed for babies and children. This niche market prioritizes safety, hypoallergenic materials, and symbolic value over the use of high-value natural gemstones.
Materials and Safety Features
When purchasing birthstone jewelry for infants or young children, the industry standards shift. Instead of delicate natural Tanzanite or brittle Zircon, manufacturers often opt for durable, synthetic alternatives that mimic the appearance of the birthstones.
- Swarovski Crystals: As noted in the product listings, "Genuine Swarovski® Crystal" is frequently used for December birthstone earrings. These are precision-cut lead glass crystals, not natural gemstones. They offer consistent sparkle and durability suitable for children's wear.
- Cubic Zirconia: Similarly, cubic zirconia is used to replicate the look of Tanzanite (often in purple hues) or Zircon (in clear or