December stands unique in the calendar of birthstones, offering not one, but four distinct gemstones to those born in the final month of the year. This abundance provides a remarkable spectrum of choice, ranging from ancient, opaque treasures to modern, brilliant faceted stones. The four recognized December birthstones are Blue Zircon, Blue Topaz, Tanzanite, and Turquoise. Each of these gems possesses a unique geological origin, a specific set of physical properties, and a rich history steeped in lore and commerce.
For the gem enthusiast, jewelry buyer, or student of gemology, understanding the nuances of these four stones is essential. They all share a dominant blue hue, a fitting tribute to the winter skies and icy landscapes associated with their month, yet their individual stories diverge significantly. From the legendary protective powers of turquoise to the recent commercial rise of blue topaz, the December birthstones offer a fascinating case study in the evolution of gemstone lore and the modern jewelry market. This article will explore the history, geological origins, gemological properties, and symbolism of each of these four remarkable gems, providing a definitive guide for anyone looking to connect with the birthstones of December.
History and Lore
The history of December's birthstones is a long and winding path, marked by ancient traditions, royal adornments, and modern marketing. The journey to the current list of four stones was not instantaneous but evolved over the 20th century, reflecting both new discoveries and commercial interests.
Turquoise, the oldest of the four, has a history stretching back millennia. It is considered the traditional December birthstone, cherished long before a formal list existed. Evidence of its use is found across ancient civilizations. The pharaohs and other rulers of ancient Egypt adorned themselves with turquoise, and Chinese artisans were carving it more than 3,000 years ago. Its appeal was not limited to the Eastern Hemisphere; the Apache people of North America believed turquoise could be found by following a rainbow to its end, and it held deep spiritual significance for many Indigenous tribes of the American Southwest. The stone’s name itself, "turquoise," is derived from the French "pierre tourques," or "Turkish stone," reflecting the trade routes that brought the gem from Persia (modern-day Iran) to Europe through Turkish markets. Persian turquoise, in particular, has been prized for centuries for its vivid, sky-blue color and minimal matrix.
The other stones joined the official list much later. In 1912, the National Association of Jewelers sought to standardize birthstones for the American market. At this time, turquoise was the primary birthstone for December. The list continued to evolve. In 1952, the Jewelry Industry Council of America updated the list, adding Blue Zircon to the December options. Zircon has a much older history as a gemstone, but its inclusion as a December birthstone is a relatively modern development. Finally, in 2002, the American Gem Trade Association (AGTA) added Tanzanite to the list, recognizing its growing popularity and significance in the gem market. Blue Topaz, while not on all official lists (such as the GIA's), is widely recognized as a modern December birthstone, having gained immense popularity in the latter half of the 20th century.
The reasons for December having four birthstones are debated. Some sources suggest it was a deliberate move to provide more affordable options for consumers, as the price points for these four gems vary dramatically. Others point to the commercial success of newly discovered or treated stones, leading to their addition over time. Regardless of the reason, this variety gives those born in December an unparalleled choice in color, durability, and price.
Geological Formation and Sources
Understanding the origins of these gems reveals the distinct geological processes that create their unique characteristics.
Turquoise is a secondary mineral formed when water containing copper and aluminum seeps through pre-existing rock. This process occurs in arid regions, where evaporation concentrates the minerals into solid form. It is typically found in veins, nodules, or botryoidal (grape-like) masses within host rock. The most significant sources include the southwestern United States (especially Arizona and New Mexico), Iran, Egypt, China, Mexico, and parts of Central Asia and Africa. The famous "Sleeping Beauty" turquoise, known for its pure, robin's-egg blue color with minimal matrix, was mined exclusively from the Sleeping Beauty Mine in Arizona before its closure. Persian turquoise from Iran is historically the most prized, celebrated for its vivid, evenly saturated sky-blue color.
Tanzanite is a relative newcomer to the gem world and is geographically unique. It is a variety of the mineral zoisite and is formed by the intense heat and pressure of the earth's crust during the formation of Mount Kilimanjaro. Its discovery is remarkably recent; it was identified in the Merelani district of Tanzania in 1967. This geographic concentration makes tanzanite exceptionally rare; it is mined only in a small, specific region of Tanzania, roughly four kilometers wide by two kilometers long. This extreme rarity is a primary driver of its value.
Blue Zircon is the oldest of these minerals in terms of its formation. Zircon is a zirconium silicate and is a primary mineral, meaning it forms directly from magma. It is found in many parts of the world, including Australia, Cambodia, Sri Lanka, Thailand, and Vietnam. A key aspect of zircon's history is its role as the oldest material on Earth, with some specimens dating back over 4 billion years, making them invaluable for geological dating. For use as a gemstone, the brownish zircon crystals are often heated to produce the desirable blue color.
Blue Topaz is a silicate mineral of aluminum and fluorine. It forms in igneous rocks, such as granite, and is often found in cavities within these rocks. Unlike tanzanite, topaz is sourced from numerous locations globally, including Sri Lanka, Brazil, Mexico, Nigeria, and the United States. Its availability in large, clean crystals makes it an abundant source for the gem trade. It is also the official state gem of Texas, a testament to its popularity in the U.S. market.
Gemological Properties
The four December birthstones vary significantly in their physical and chemical properties, which directly impacts their durability, appearance, and care requirements.
Hardness and Durability
The hardness of a gemstone, measured on the Mohs scale from 1 (softest) to 10 (hardest), is a critical factor for jewelry intended for regular wear.
- Blue Topaz is the most durable of the four, with a hardness of 8 on the Mohs scale. This makes it an excellent choice for rings and other jewelry that may be subject to daily knocks.
- Blue Zircon has a hardness of 6.5 to 7.5. While reasonably durable, it is more susceptible to scratches and chipping than topaz. Its brittle nature means it should be protected in jewelry settings.
- Tanzanite is significantly softer, with a hardness of 6.5 to 7. It also has perfect cleavage in one direction, meaning it can split if struck with force. This property makes it a better choice for earrings, pendants, or occasional-wear rings rather than everyday rings.
- Turquoise is the softest of the group, with a hardness of 5 to 6. It is also porous and can be susceptible to damage from chemicals, lotions, and even skin oils. This requires the most careful handling and maintenance.
Color and Clarity
All four stones are prized for their blue hues, but the shades and transparency differ.
- Turquoise is typically semi-translucent to opaque. Its color ranges from sky blue to greenish blue, often interrupted by dark veining known as "matrix." Highly prized varieties, such as Persian and Sleeping Beauty turquoise, feature a vibrant, even color with minimal to no matrix.
- Tanzanite is known for its unique and vibrant blue-to-violet hue, often displaying a strong pleochroism (showing different colors when viewed from different angles). It is typically a transparent to translucent gem.
- Blue Zircon is known for its high brilliance and fire, which can rival that of diamond. It is typically transparent and can be found in a range of blue shades, from pale to deep, intense blue.
- Blue Topaz in its natural state is typically a very pale blue. The intense, deep blue color seen in most commercial jewelry is the result of irradiation and heat treatment. It is prized for its clarity and transparency.
Chemical Composition and Treatment
- Turquoise is a hydrous phosphate of copper and aluminum. Its color is directly influenced by the amount of copper present.
- Tanzanite is a variety of zoisite, an aluminum silicate mineral, with its blue-to-violet color caused by trace amounts of vanadium.
- Blue Zircon is zirconium silicate (ZrSiO₄). The blue color in most gem-grade zircon is achieved through the heating of brownish crystals.
- Blue Topaz is aluminum silicate fluoride hydroxide (Al₂SiO₄(F,OH)₂). The vast majority of blue topaz on the market has been treated to achieve its color.
Comparative Gemological Table
| Gemstone | Chemical Composition | Mohs Hardness | Typical Treatment | Key Sources |
|---|---|---|---|---|
| Blue Topaz | Al₂SiO₄(F,OH)₂ | 8 | Irradiation, Heat | Brazil, Nigeria, Sri Lanka, U.S. |
| Blue Zircon | ZrSiO₄ | 6.5 - 7.5 | Heat | Australia, Cambodia, Vietnam, Sri Lanka |
| Tanzanite | Ca₂Al₃(SiO₄)₃(OH) | 6.5 - 7 | Heat | Tanzania (only source) |
| Turquoise | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5 - 6 | Stabilization, Dyeing | U.S. (Arizona), Iran, Egypt, China |
Symbolism and Metaphysical Beliefs
Across cultures and centuries, these gemstones have been imbued with powerful meanings and supposed metaphysical properties.
Turquoise is perhaps the most legendary in this regard. It was thought to possess many beneficial powers, guaranteeing health and good fortune. From the 13th century onward, it was believed to protect the wearer from falling, particularly from horses, and would break into several pieces at the approach of a disaster, serving as a warning. Hindu mystics believed that seeing a turquoise after beholding the new moon would ensure fantastic wealth. Today, it continues to symbolize wisdom, tranquility, and friendship.
Tanzanite, being a new discovery, has a more modern set of associations. It is often linked to transformation, making it a popular stone for those marking a new beginning or seeking a higher consciousness. It is also associated with clarity and calm.
Blue Zircon is historically associated with prosperity and honor. It was believed to bring wisdom and to protect travelers from injury and disease. Its brilliant sparkle was thought to ward off evil spirits and bring peace to its wearer.
Blue Topaz is linked to calm, clarity, and communication. It is often associated with love and affection and is believed to help soothe tempers and promote understanding. Its clear, cool color is seen as a reflection of a clear mind and peaceful spirit.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of December's birthstones, with requirements varying based on their hardness and stability.
- Blue Topaz: Due to its hardness of 8 and lack of cleavage, blue topaz is quite durable. It can be safely cleaned with warm water, a small amount of mild soap, and a soft brush. It is generally safe for ultrasonic and steam cleaners, though it's always best to check with a professional if the stone is set in a delicate piece.
- Blue Zircon: Although relatively hard, zircon is brittle. Avoid ultrasonic cleaners and steam cleaners, as the vibrations and rapid temperature changes can cause fractures. The best cleaning method is warm, soapy water and a soft brush.
- Tanzanite: With its lower hardness and perfect cleavage, tanzanite requires gentle handling. It should never be put in an ultrasonic cleaner or steam cleaner. Clean it only with warm, soapy water and a soft cloth. It is best removed before any physical activity.
- Turquoise: This is the most delicate of the four. It is porous and can be damaged by chemicals, including those found in cosmetics, lotions, and even sweat. It should be wiped clean with a soft, dry cloth. Avoid water, soap, and all commercial cleaners. Turquoise is often treated or stabilized to improve its durability, but it still requires careful handling to prevent discoloration or damage.
Conclusion
The four birthstones of December—Blue Zircon, Blue Topaz, Tanzanite, and Turquoise—collectively offer a rich palette of blue that captures the essence of the winter month. They represent a unique convergence of ancient history and modern gemology, from the multi-millennial legacy of turquoise to the geologically recent discovery of tanzanite. Each stone presents a distinct profile in terms of durability, value, and symbolism, allowing for a deeply personal choice. Whether one is drawn to the traditional protective lore of turquoise, the brilliant fire of zircon, the rare violet hue of tanzanite, or the accessible clarity of blue topaz, the gems of December provide a meaningful and beautiful connection to the natural world and the traditions of birthstones.