December is a unique month in the calendar of birthstones, distinguished by its association with not one, but four distinct gemstones: blue zircon, blue topaz, tanzanite, and turquoise. This abundance of choice is unparalleled among the months, offering individuals born in December a remarkable spectrum of color, history, and meaning. All four stones share a dominant blue hue, a visual echo of the winter skies and icy landscapes of their namesake month. This article delves into the rich tapestry of these four December birthstones, exploring their geological origins, gemological properties, historical lore, and practical care, drawing exclusively from authoritative sources to provide a definitive guide for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore: A Blend of Ancient and Modern
The tradition of assigning gemstones to months has deep roots in ancient cultures, and the December birthstones reflect a fascinating blend of millennia-old gems and more recent discoveries. Turquoise stands as one of the most ancient gems in this quartet. It has been cherished for thousands of years, adorning the pharaohs of ancient Egypt and being carved by Chinese artisans over 3,000 years ago. Its historical significance is woven into the fabric of numerous cultures. For instance, it played a vital role in the lives of Native American tribes, with the Apache believing that turquoise could be found by following a rainbow to its end. Across the globe, in the 13th century, a potent belief emerged that turquoise could protect the wearer from falling, particularly from horses, and that the stone would shatter into several pieces as a warning of impending disaster. Hindu mystics held that seeing a turquoise after beholding the new moon would ensure fantastic wealth. The stone was also thought to guarantee health and good fortune, promote happiness, peace, and positive energy, and serve as a powerful spiritual talisman.
Zircon, another of the December stones, also carries a long and storied history. The word’s origin is debated; some scholars trace it to the Arabic zarkun (cinnabar or vermilion), while others point to the Persian zargun (gold colored), a fitting description given zircon’s diverse color palette, which includes red, orange, yellow, brown, green, and blue. During the Middle Ages, zircon was believed to have the power to lull one into a deep sleep and to scare off evil spirits. In the Hindu religion, zircon is one of the nine gems of the navaratna, a sacred collection that, when worn together, is said to protect the wearer and bestow wealth, wisdom, and good health. Colorless zircon, known for its exceptional brilliance and flashes of multicolored light called "fire," was historically confused with diamond, a testament to its dazzling optical properties. In the Victorian era, blue zircon was particularly favored.
The other two December birthstones are relative newcomers to the official list, reflecting the evolving nature of gemology and market demand. In 1912, the National Association of Jewelers standardized the unofficial American birthstones, creating a list that combined ancient customs with gems practical for jewelry companies to sell. The list continued to evolve; in 1952, the Jewelry Industry Council of America updated it, adding zircon to December’s offerings. The most recent addition is tanzanite, which was officially added to the December birthstone list in 2002. This progression highlights how birthstone traditions can adapt, incorporating new discoveries and commercial offerings. The reason for December having so many birthstones is not definitively known, but some sources suggest it was to provide more affordable options for consumers.
Geological Formation and Global Sources
The four December birthstones originate from vastly different geological environments and are mined in specific regions around the world.
Turquoise is a secondary mineral that forms in arid regions where acidic, copper-rich groundwater percolates through pre-existing rocks containing aluminum and phosphorus. Over geological time, this process precipitates turquoise in nodules or veins within the host rock. The presence of various trace elements and the host rock itself often results in distinctive brown or black veins, known as matrix, running through the gem. Turquoise is mined in several locations, though specific countries are not detailed in the provided sources beyond its historical use in Egypt and China.
Zircon is a mineral belonging to the nesosilicate group and is one of the oldest minerals on Earth, often found as crystals within igneous and metamorphic rocks. The blue variety, which is popular as a December birthstone, is typically achieved through heat treatment of brown zircon. The sources do not specify primary mining locations for zircon, but its global occurrence is well-documented in geological literature.
Tanzanite is exceptionally rare, being mined in only one region on the planet: the Merelani Hills of northern Tanzania. Its formation is linked to the unique geological conditions of the East African Rift, where the gem forms in hydrothermal veins within a specific type of metamorphic rock. This extreme rarity is a key factor in its value and desirability.
Blue Topaz is mined in several countries, including Sri Lanka, Brazil, Mexico, Nigeria, and the United States. It is notably the official state gem of Texas. Topaz forms in igneous rocks like granite and rhyolite, often in cavities or veins. The blue color in most commercial blue topaz is the result of irradiation and heat treatment applied to colorless or pale yellow topaz, a common and accepted industry practice.
Gemological Properties: A Scientific Comparison
Understanding the physical and optical properties of these gems is crucial for appreciating their beauty, durability, and care requirements. The following table synthesizes the key gemological data for each December birthstone as provided in the sources.
| Gemstone | Hardness (Mohs Scale) | Color | Refractive Index | Specific Gravity | Transparency | Cleavage | Durability |
|---|---|---|---|---|---|---|---|
| Blue Topaz | 8 | Blue (natural or heat-treated) | 1.62–1.64 | 3.5–3.6 | Transparent to translucent | None | High; suitable for everyday wear |
| Turquoise | 5–6 | Blue to green | 1.61–1.65 | 2.6–2.8 | Opaque | None | Low to moderate |
| Tanzanite | 6–7 | Blue to violet | 1.694–1.701 | 3.18–3.38 | Transparent | Perfect in one direction | Moderate |
| Zircon | 7.5–8 | Blue (heat-treated), yellow, brown, red | 1.92–2.00 | 4.6–4.7 | Transparent to translucent | None | High |
Blue Topaz is the most durable of the four for everyday wear, with a hardness of 8 on the Mohs scale, making it resistant to scratches. It has no cleavage, which adds to its toughness. However, it can be damaged by high heat or harsh chemicals.
Turquoise, with a hardness of only 5–6, is the softest and most fragile of the group. It is porous and can easily be scratched or chipped. It is sensitive to changes in moisture and temperature and can absorb oils and dyes, which may alter its color. Its opacity and potential matrix inclusions give it a distinct, earthy appearance.
Tanzanite has a moderate hardness of 6–7 but possesses a perfect cleavage in one direction. This means it is highly prone to chipping or breaking if struck with force, especially along that cleavage plane. Its vibrant blue-to-violet color is highly prized, and its transparency allows for excellent light performance.
Zircon is a highly durable gemstone with a hardness of 7.5–8, just below topaz. It has no cleavage, making it tough. Its most remarkable feature is its high refractive index (1.92–2.00), which gives it exceptional brilliance and fire, often surpassing that of diamond. The blue variety is particularly sought after for December.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, all four December birthstones are imbued with deep symbolic meaning and metaphysical beliefs that have persisted through centuries.
Turquoise is widely regarded as a stone of protection, healing, and good fortune. Its symbolism is particularly strong in Native American cultures, where it is considered a sacred stone. It is believed to promote positive energy, happiness, peace, and spirituality. The ancient belief that it could shatter to warn of danger underscores its role as a protective talisman.
Zircon is associated with wisdom, wealth, and spiritual protection. As one of the nine gems in the Hindu navaratna, it is part of a powerful collective for protection and well-being. Historically, it was thought to ward off evil spirits and promote restful sleep. Its brilliant fire is often linked to clarity of thought and spiritual illumination.
Tanzanite, as a modern addition, carries symbolism tied to its rarity and unique origin. It is often associated with transformation, new beginnings, and the discovery of one's unique destiny, mirroring its singular geographic source. Its mesmerizing color is said to stimulate the imagination and encourage a higher consciousness.
Blue Topaz, with its cool, serene hue, is frequently connected to calmness, clarity of communication, and emotional balance. Its durability and clarity make it a symbol of steadfastness and truth. The stone’s association with the state of Texas adds a layer of regional pride and identity to its symbolism.
Care and Cleaning: Preserving the Gems
Proper care is essential to maintain the beauty and longevity of these birthstones, with requirements varying significantly based on their gemological properties.
Blue Topaz and Zircon, being the hardest and most durable, can withstand gentle cleaning with warm, soapy water and a soft brush. They should be protected from sharp blows and extreme temperatures. Ultrasonic and steam cleaners are generally safe for these stones, but it is always best to consult a jeweler if unsure.
Turquoise requires the most careful handling. Due to its porosity and softness, it should be cleaned only with a soft, dry cloth. Avoid water, chemicals, and ultrasonic cleaners, as these can damage the stone, cause discoloration, or loosen any matrix. It is best suited for occasional wear in protective settings like pendants or earrings.
Tanzanite is best cleaned with warm, soapy water and a soft cloth. Ultrasonic and steam cleaners are never recommended for tanzanite due to its perfect cleavage, which makes it vulnerable to fracture from vibration and heat. Because of its moderate hardness and cleavage, it is most safely set in earrings or pendants. If worn in a ring, a protective setting (such as a bezel or halo) is strongly advised, and it should not be worn for daily, rough tasks.
Conclusion
The four birthstones of December—blue zircon, blue topaz, tanzanite, and turquoise—offer an extraordinary range of choices that cater to every preference, budget, and style. From the ancient, protective lore of turquoise and zircon to the modern rarity of tanzanite and the durable brilliance of blue topaz, each stone tells a unique story. Their shared blue color palette connects them to the winter season, while their distinct geological origins, physical properties, and cultural significance make them individually compelling. Understanding their histories, scientific characteristics, and care requirements allows one to make an informed and meaningful choice, ensuring that a December birthstone remains a cherished possession for a lifetime.