The month of December is uniquely associated with three distinct gemstones: zircon, tanzanite, and turquoise. This trio offers a remarkable spectrum of color and character, from the brilliant fire of zircon to the velvety blue of tanzanite and the opaque, earthy tones of turquoise. While traditionally celebrated as birthstones, these gems have also become increasingly popular choices for engagement rings, symbolizing unique personal style and enduring love. This article explores the properties, origins, and considerations for selecting these December gems, drawing from contemporary jewelry market insights and gemological understanding.
The Modern December Trio: An Overview
The American Gem Society (AGS) and the American Gem Trade Association (AGTA) have recognized multiple stones for December, reflecting the gem's historical evolution and market availability. Zircon, not to be confused with cubic zirconia, is one of the oldest minerals on Earth, prized for its exceptional brilliance and fire. Tanzanite, a relative newcomer discovered in 1967, captivates with its unique trichroic color palette. Turquoise, a hydrated phosphate of copper and aluminum, has been cherished for millennia for its distinctive sky-blue to green hues. The choice among these stones often depends on personal preference for color, durability, and budget.
When considering these stones for an engagement ring—a piece meant to be worn daily—their physical properties are paramount. Durability, particularly hardness and resistance to chipping or cracking, is a key factor in ensuring the ring can withstand daily wear. The following sections delve into each gemstone's specific characteristics, supported by available data.
Zircon: The Brilliance of Ancient Earth
Zircon is a naturally occurring zirconium silicate (ZrSiO₄) and is one of the hardest minerals, scoring an 8 on the Mohs scale of hardness. This makes it an excellent candidate for jewelry that will be worn regularly, such as an engagement ring, as it is resistant to scratching from everyday abrasives. Its most celebrated property is its high refractive index (1.92-1.98) and strong dispersion (0.039), which gives it a brilliant sparkle and fiery "fire" that can rival diamond. Zircon occurs in a variety of colors, with blue, golden, and green being the most common, though heat treatment can produce a range of hues from colorless to yellow, brown, and red.
Geological Formation and Sources
Zircon is a detrital mineral, meaning it is often found in sedimentary deposits derived from the weathering of igneous and metamorphic rocks. It is a common accessory mineral in many rock types and is highly resistant to chemical and physical weathering, making it one of the oldest materials on Earth. Major commercial sources include Cambodia, Sri Lanka, and Thailand, with other deposits in Australia, Norway, and the United States. The gemological community often refers to "Jacinth" as an old name for zircon, particularly the brownish-red varieties.
Gemological Properties and Considerations
Zircon's hardness of 8 makes it suitable for most jewelry settings, though its perfect cleavage in one direction requires careful cutting and setting to avoid impact damage. It is important to note that zircon is often heat-treated to achieve a more desirable color (e.g., to transform brownish zircon into a colorless or blue stone). This treatment is standard and widely accepted in the gem trade. When selecting a zircon for an engagement ring, clarity is typically high, as zircon is generally clean and transparent. Its brilliance and fire make it a stunning centerpiece, especially in solitaire or halo settings.
Tanzanite: The Singular Blue of Merelani
Tanzanite (a variety of the mineral zoisite) is a member of the epidote group and is composed of calcium aluminum hydroxyl silicate. It is valued for its strong violet-blue to purplish-blue color, which is often the result of heat treatment (a standard practice that permanently enhances its color). Tanzanite is pleochroic, displaying three different colors (blue, violet, and burgundy) depending on the viewing angle, which adds to its visual interest. On the Mohs scale, tanzanite ranks at 6 to 6.5, making it relatively soft and more susceptible to scratches and impacts compared to zircon or diamond. This necessitates careful handling and protective settings for engagement rings.
Geological Formation and Sources
Tanzanite is found in only one location in the world: the Merelani Hills of Northern Tanzania. Its formation is linked to a unique geological event involving the heating and chemical alteration of zoisite crystals by contact with manganese-bearing fluids. The limited geographic source makes tanzanite a rare gemstone. Its discovery in 1967 by a local prospector, followed by its promotion by Tiffany & Co. in 1968, established its status as a modern gemstone.
Gemological Properties and Considerations
Tanzanite's color is its defining feature, ranging from light lavender to deep royal blue. The most valuable stones exhibit a rich, vivid blue with minimal violet overtones. Due to its lower hardness and perfect cleavage, tanzanite requires protective settings for rings, such as bezel settings or halo designs that shield the stone from side impacts. It is also sensitive to rapid temperature changes and ultrasonic cleaners, so gentle cleaning with a soft brush and mild soap is recommended. For an engagement ring, selecting a tanzanite with a secure, low-profile setting is advisable to minimize the risk of damage.
Turquoise: The Ancient Sky Stone
Turquoise is an opaque, blue-to-green mineral composed of hydrated copper and aluminum phosphate. Its color ranges from sky blue to greenish blue, often with a distinctive matrix (veins of the host rock, such as iron or limonite) running through it. Turquoise is relatively soft, ranking 5 to 6 on the Mohs scale, and is porous, meaning it can absorb oils, cosmetics, and chemicals, which may alter its color over time. This porosity also makes it susceptible to breaking and chipping, requiring careful handling and maintenance.
Geological Formation and Sources
Turquoise forms in arid regions where acidic water percolates through rocks containing copper, aluminum, and phosphorus. It is often found in association with copper deposits. Notable sources include the United States (Nevada, Arizona, New Mexico), Iran, China, and Egypt. The stone has been used for thousands of years, with evidence of its use in ancient Egypt, Mesopotamia, and the Americas. American turquoise, particularly from the Nevada region, is highly valued for its range of colors and matrix patterns.
Gemological Properties and Considerations
Turquoise's opacity and unique color make it a distinctive choice for jewelry. It is often cut into cabochons (dome-shaped stones) to showcase its color and matrix. For engagement rings, turquoise requires a protective setting, such as a bezel or channel setting, to shield it from impact and abrasion. It should never be exposed to harsh chemicals, perfumes, or prolonged water exposure. Cleaning should be done with a soft, dry cloth; ultrasonic and steam cleaning are not recommended. Due to its softness, turquoise rings are best suited for occasional wear rather than daily use, though many choose it for its symbolic and aesthetic value.
Symbolism and Metaphysical Beliefs
Each December birthstone carries a rich history of symbolism and metaphysical beliefs, which add to their allure as engagement ring stones.
- Zircon: Historically, zircon was believed to promote honor, purity, and wisdom. It was often used as a protective talisman and was said to aid in sleep and ward off evil spirits. Its brilliance and fire were associated with clarity of thought and spiritual light.
- Tanzanite: As a modern gemstone, tanzanite is associated with transformation and new beginnings. It is often linked to the crown chakra in spiritual practices, believed to facilitate communication, intuition, and spiritual awakening. Its discovery in the 20th century lends it an aura of rarity and uniqueness.
- Turquoise: One of the most ancient gems, turquoise is a symbol of protection, health, and good fortune. It has been worn by warriors, royalty, and spiritual leaders across cultures. In many Native American traditions, turquoise is a sacred stone representing the sky and water, and is believed to bring peace and balance.
Care and Maintenance for Engagement Rings
Proper care is essential for maintaining the beauty and integrity of any gemstone, especially in a ring intended for daily wear. The following guidelines are based on the gemological properties of each December stone.
| Gemstone | Mohs Hardness | Key Vulnerabilities | Recommended Setting | Cleaning Method |
|---|---|---|---|---|
| Zircon | 8 | Perfect cleavage; avoid sharp blows | Prong, bezel, or halo | Warm soapy water, soft brush. Avoid ultrasonic cleaners if heavily included. |
| Tanzanite | 6 - 6.5 | Cleavage; low hardness; sensitive to heat | Protective bezel or halo; avoid high-prong settings | Warm soapy water, soft brush. Avoid ultrasonic cleaners, steam, and sudden temperature changes. |
| Turquoise | 5 - 6 | Porosity; softness; susceptible to chemicals and impact | Bezel or channel setting; low profile | Dry, soft cloth. Avoid water, chemicals, and ultrasonic cleaners. |
General Advice: It is recommended to remove any gemstone ring before activities involving impact, chemicals, or abrasives (e.g., gardening, cleaning, sports). Regular professional inspections by a jeweler are advised to check the security of the setting and the condition of the stone.
Selecting a December Gemstone for an Engagement Ring
Choosing between zircon, tanzanite, and turquoise for an engagement ring involves balancing aesthetic preference with practical considerations. Zircon offers exceptional brilliance and durability, making it a practical yet stunning choice for a daily-wear ring. Tanzanite provides a unique, captivating color but requires a more protective setting and careful wear due to its lower hardness. Turquoise offers a bold, earthy aesthetic with deep cultural roots but is the least durable of the three, best suited for rings worn occasionally or with the understanding that it may show wear over time.
The decision ultimately rests on the wearer's lifestyle, personal connection to the stone's color and meaning, and willingness to provide the necessary care. Consulting with a reputable jeweler who can provide certified stones and secure settings is crucial for ensuring the longevity and beauty of the ring.
Conclusion
The December birthstones—zircon, tanzanite, and turquoise—provide a diverse palette for engagement rings, each with its own geological story, physical properties, and symbolic significance. From the ancient, fiery brilliance of zircon to the singular blue of tanzanite and the timeless, protective qualities of turquoise, these gems offer meaningful alternatives to traditional engagement ring stones. Understanding their unique characteristics, from hardness and cleavage to care requirements, allows for an informed and cherished choice. Whether selected for its durability, color, or cultural lore, a December gemstone ring is a testament to individuality and enduring commitment.