The month of December is uniquely represented in the world of gemstones by a trio—or, by some accounts, a quartet—of blue-hued treasures. Unlike most months, which are associated with a single birthstone, December offers a diverse palette of blue, from the sky-like clarity of zircon to the deep, shifting violet of tanzanite, the earthy turquoise, and the accessible brilliance of blue topaz. This variety provides a wealth of choice for those born in the winter month, allowing for personal expression through color and style. The December birthstones—turquoise, tanzanite, zircon, and blue topaz—each possess a distinct geological origin, a unique history, and a set of gemological properties that make them worthy of study and admiration. This article delves into the history, formation, properties, and symbolism of these captivating blue gems, offering a detailed exploration for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore: The Journey to a Modern Birthstone
The concept of birthstones has ancient roots, with traditions tracing back to civilizations in Egypt, Greece, and Rome, where gemstones were believed to hold mystical and healing properties. The modern list of birthstones, however, is a more recent development. In 1912, the National Association of Jewelers in the United States standardized an unofficial list, blending historical customs with gemstones deemed practical for the jewelry trade. This list has been updated over time, reflecting new discoveries and market trends.
For December, the historical tradition is most strongly linked to turquoise. The name "turquoise" itself derives from the French pierre turquoise, meaning "stone of Turkey," as the gem was introduced to Europe through Turkish bazaars. Its use dates back millennia, with ancient cultures valuing it for its distinctive color and believed protective powers.
The other December stones were added later to expand the color options and accommodate new gemological finds. In 1952, the Jewelry Industry Council of America updated the list, adding zircon to December’s offerings. Zircon has a much longer history as a gemstone, valued for its brilliance and fire, but its inclusion as a December birthstone is a modern designation. The most recent addition is tanzanite, which was added in 2002. This timing reflects tanzanite's discovery in the 20th century and its rapid rise in popularity within the jewelry market.
Blue topaz, while not one of the three traditional birthstones for December (turquoise, tanzanite, and zircon), is frequently cited as a modern or alternative birthstone for the month, particularly in the United States. Its inclusion is largely due to its wide availability, durability, and beautiful blue hue, which makes it a practical and attractive option for jewelry.
The reason December has multiple birthstones is not definitively documented in the provided sources. However, it is suggested that the variety was introduced to offer more affordable options and a broader range of colors and styles to consumers. The evolution of the birthstone list, as seen with the addition of tanzanite, also indicates that the list is not static but adapts to new gemstones entering the market and gaining commercial significance.
Geological Formation and Global Sources
The diverse December birthstones originate from vastly different geological processes and locations, contributing to their unique characteristics and value.
Turquoise is an opaque, secondary mineral that forms in arid regions where groundwater containing copper seeps into bedrock. Over time, reactions with other minerals create the stunning blue-to-green stone. The distinctive dark lines and shapes within turquoise, known as matrix, are remnants of the surrounding rock. While turquoise has been mined for thousands of years, major sources today include the United States (particularly Arizona and New Mexico), Iran, and Egypt. The specific mineral content and geological conditions of each location influence the stone's color and matrix pattern.
Tanzanite is a relative newcomer to the gemological world. It is a variety of the mineral zoisite and is prized for its rich violet-blue color. Its geological formation is exceptionally rare. Tanzanite is found in only one location on Earth: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. This extreme rarity is a primary factor in its high value and cost. The stones are formed through a complex process involving heat and pressure acting on zoisite crystals, a phenomenon unique to this specific geographic area.
Zircon is one of the oldest minerals on Earth, with crystals found in geologically ancient rocks. It is a zirconium silicate and forms in a variety of environments, including igneous and metamorphic rocks. While zircon occurs in many colors, the blue variety used as a December birthstone is typically heat-treated to achieve its vibrant hue. Major sources for gem-quality zircon include Sri Lanka, Cambodia, Thailand, and Australia. Its durability and brilliance have made it a valued gem for centuries.
Blue Topaz is a silicate mineral that forms in igneous rocks, particularly in large, cavity-rich granitic pegmatites. Its natural blue color is typically very light, and most of the commercially available blue topaz on the market has been treated by irradiation and heat to achieve its deeper, more desirable shades of blue, such as Swiss Blue and London Blue. It is mined in several countries, including Sri Lanka, Brazil, Mexico, Nigeria, and the United States. It is notably the official state gem of Texas.
Gemological Properties: A Scientific Comparison
Understanding the physical and chemical properties of these gemstones is crucial for both appreciation and practical care. The table below summarizes key gemological data for the primary December birthstones, based on the information provided in the sources.
| Gemstone | Chemical Composition | Mohs Hardness | Key Characteristics | Typical Treatment |
|---|---|---|---|---|
| Turquoise | Hydrated copper aluminum phosphate | 5 - 6 | Opaque, often with matrix (veining), color ranges from sky blue to greenish blue. | Stabilization (impregnation with resin or wax) is common. |
| Tanzanite | Calcium aluminum hydroxyl sorosilicate (Zoisite) | 6.5 - 7 | Trichroic (shows three colors: blue, violet, and burgundy), transparent to translucent. | Heat treatment is standard to enhance blue color. |
| Zircon | Zirconium silicate | 6.5 - 7.5 | High refractive index and strong dispersion ("fire"), can be brittle. | Heat treatment to achieve blue color (often from brown or colorless zircon). |
| Blue Topaz | Aluminum fluorosilicate | 8 | Transparent, vitreous luster, durable. | Irradiation followed by heat treatment to produce blue color. |
Turquoise is the softest of the group, with a hardness of 5 to 6 on the Mohs scale. Its opacity and porous nature make it susceptible to damage and discoloration. It is almost always treated to improve durability and color stability.
Tanzanite has a hardness of 6.5 to 7, making it relatively durable but still susceptible to chipping or cracking if struck. Its most remarkable property is its trichroism—under different crystal directions, it can appear blue, violet, or burgundy. This dynamic color play is a hallmark of the stone.
Zircon is known for its exceptional brilliance and fire, which can rival that of diamond. It has a high refractive index and strong dispersion. However, it can be brittle due to its crystal structure, making it more prone to chipping than other gems of similar hardness. The blue zircon used in jewelry is typically produced by heat-treating natural zircon crystals.
Blue Topaz is the hardest and most durable of the December birthstones, with a Mohs hardness of 8. This makes it an excellent choice for jewelry that will be worn daily, such as rings. Its transparency and vitreous luster allow for brilliant sparkle when cut properly. As noted, virtually all blue topaz on the market has been treated to achieve its color.
Symbolism and Metaphysical Beliefs
Across cultures and centuries, gemstones have been imbued with symbolic meaning and metaphysical properties. The December birthstones are no exception, each carrying its own set of beliefs.
Turquoise is historically associated with protection, good fortune, and healing. Many cultures, including ancient Persians and Native American tribes, believed it could ward off evil and bring luck to the wearer. It is often linked to tranquility, serenity, and emotional balance. Its connection to water and sky reinforces its symbolism of life and purity.
Tanzanite, a modern gem, has quickly developed its own lore. It is often described as a stone of transformation, spiritual awakening, and new beginnings. Its discovery in the 20th century aligns with its symbolism of moving forward and embracing change. Some believe it facilitates a higher consciousness and clearer communication.
Zircon has been associated with wisdom, clarity, and honor. In medieval times, it was thought to promote rest and ward off evil spirits. Its brilliant sparkle is linked to purity and light. Today, it is sometimes considered a stone of prosperity and grounding.
Blue Topaz is frequently connected to calm, communication, and emotional balance. It is said to soothe tempers, enhance clarity of thought, and promote truthful expression. Its cool blue color evokes feelings of peace and tranquility, making it a popular choice for those seeking mental and emotional harmony.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of any gemstone. The December birthstones, with their varying properties, require specific handling.
Turquoise demands the most careful treatment. Due to its softness and porosity, it should be protected from chemicals, perfumes, and cosmetics, which can cause discoloration. Clean it gently with a soft, dry cloth. Avoid ultrasonic cleaners, steam cleaners, and prolonged exposure to water, as these can damage the stone or any stabilizing treatments.
Tanzanite is relatively durable but can be sensitive to sharp blows and rapid temperature changes. It is best cleaned with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaning, which can cause fractures. Given its cleavage, it should be stored carefully to prevent scratching.
Zircon, while hard, is brittle. It should be protected from hard impacts that could cause chipping. Clean it with warm, soapy water and a soft brush. Ultrasonic cleaners are generally safe for untreated zircon, but caution is advised for treated stones. Avoid sudden temperature changes.
Blue Topaz, being the hardest and most durable, is well-suited for everyday wear. It can be cleaned with warm, soapy water and a soft brush. It is generally safe for ultrasonic cleaning, but it is always prudent to check with a professional jeweler, especially if the stone is set in a delicate setting. Avoid harsh chemicals and extreme heat.
Conclusion
December’s birthstones offer a remarkable spectrum of blue, from the ancient, earthy turquoise to the rare, transformative tanzanite, the brilliant, fiery zircon, and the durable, serene blue topaz. Each gemstone tells a distinct story of geological formation, historical significance, and cultural symbolism. While turquoise holds the longest tradition as December’s stone, the additions of zircon, tanzanite, and blue topaz have enriched the options available to those born in the winter month, providing choices based on color preference, budget, and personal meaning. Understanding the unique properties and care requirements of each stone allows for a deeper appreciation of these beautiful gems and ensures they can be cherished for generations to come. Whether chosen for its historical lore, its metaphysical properties, or simply its captivating color, a December birthstone is a timeless and personal emblem of the month.