December is a unique month in the world of birthstones, possessing not one, but a selection of gems traditionally associated with those born within its span. While modern lists prominently feature turquoise, zircon, and tanzanite, the historical record reveals a more complex lineage, including ruby and other regional variations. This article will explore the history, geological origins, gemological properties, and cultural significance of these December birthstones, drawing upon available historical and gemological information.
A Shifting Lineage: Historical Perspectives
The designation of birthstones has evolved considerably over time. Early associations, inspired by Biblical texts, initially linked ruby with December. This connection persisted for centuries, with ruby believed to sharpen the mind, improve concentration, and encourage feelings of courtly love. However, as gemological understanding and trade routes expanded, the list of December birthstones began to diversify.
By 1870, Tiffany & Co.’s “Gregorian Birthstone Poems” pamphlet had established turquoise as a December birthstone. This association was further solidified in 1912 by the National Association of Jewellers (now Jewellers of America), which listed turquoise as the primary stone and lapis lazuli as an alternative. The mid-20th century saw further changes, with zircon being added to the list in 1952 by the Jewelry Industry Council of America. Most recently, in 2002, tanzanite was officially recognized as a December birthstone in the United States. This evolution reflects both changing aesthetic preferences and the discovery of new and captivating gemstones.
The reasons for multiple birthstones assigned to a single month are rooted in this historical evolution. Birthstone lists have been revised and updated over time, and December’s gemstones have undergone perhaps the most significant transformations. The consistent presence of turquoise throughout much of this history suggests its enduring appeal and cultural significance.
Geological Formation and Sources
The December birthstones originate from diverse geological settings around the globe. Turquoise, a hydrated phosphate of copper and aluminum, forms through a process of weathering and hydrothermal activity. It is typically found in arid regions, often associated with copper deposits. Significant sources include the southwestern United States, Iran, and China.
Zircon, a zirconium silicate, is a remarkably durable mineral found in a variety of igneous and metamorphic rocks. It is mined in Thailand, Cambodia, and Vietnam, among other locations. Notably, zircon contains trace amounts of uranium and thorium, making it invaluable for radiometric dating and revealing that some specimens are over 4.4 billion years old – among the oldest minerals on Earth.
Tanzanite, a relatively recent discovery, is a variety of the mineral zoisite. It is found exclusively in a small area near Mount Kilimanjaro in Tanzania, making it a geographically unique gemstone. Its formation is linked to the complex geological processes associated with the East African Rift Valley.
Ruby, historically linked to December, forms in metamorphic rocks and alluvial deposits. Primary sources include Myanmar (Burma), Thailand, and Sri Lanka.
Gemological Properties
Each December birthstone possesses distinct gemological properties that contribute to its unique beauty and value.
Turquoise: Its color ranges from sky blue to greenish-blue, influenced by the presence of copper and iron. It typically exhibits a waxy luster and a hardness of 5-6 on the Mohs scale.
Zircon: Available in a spectrum of colors, blue zircon is the most popular variety for December. It boasts a high refractive index, contributing to its brilliance, and a hardness of 6.5-7.5 on the Mohs scale.
Tanzanite: Characterized by its vibrant violet-blue hues, tanzanite displays strong pleochroism, meaning it exhibits different colors when viewed from different angles. Its hardness is 6-7 on the Mohs scale.
Ruby: Renowned for its intense red color, ruby is a variety of corundum (aluminum oxide). It possesses exceptional hardness, registering 9 on the Mohs scale, making it highly durable.
Here's a comparative table summarizing key properties:
| Gemstone | Chemical Composition | Hardness (Mohs) | Color | Notable Features |
|---|---|---|---|---|
| Turquoise | Hydrated Phosphate of Copper and Aluminum | 5-6 | Sky Blue to Greenish-Blue | Waxy Luster |
| Zircon | Zirconium Silicate | 6.5-7.5 | Blue, Golden, Red, Clear | High Refractive Index |
| Tanzanite | Calcium Aluminum Silicate (Zoisite) | 6-7 | Violet-Blue | Strong Pleochroism |
| Ruby | Aluminum Oxide | 9 | Red | Exceptional Durability |
Symbolism and Metaphysical Beliefs
Throughout history, each of these gemstones has been imbued with symbolic meaning and metaphysical properties. Turquoise has long been considered a talisman of protection, prosperity, and luck, particularly valued by ancient shamans. It is also associated with Sagittarius, one of the zodiac signs of December.
Blue zircon is believed to encourage joy and emotional balance. Turquoise is cherished for its spiritual and healing qualities, while blue topaz is thought to promote wisdom and new beginnings. Tanzanite is considered a protective and soothing stone, facilitating the sharing of spiritual insights.
Historically, ruby symbolized courage and passion, while chrysoprase (an older Russian December birthstone) was believed to bring good fortune and mend broken hearts. Onyx, the Tibetan birthstone for December, offered self-mastery and protective energy, and bloodstone was a stone of courage and revitalization.
Care and Cleaning
Proper care is essential to maintain the beauty and integrity of these December birthstones. Due to its relative softness, turquoise is susceptible to scratching and should be protected from harsh impacts. Cleaning can be done with a soft cloth and mild soapy water. Zircon and tanzanite, with their higher hardness, are more durable but should still be handled with care. Avoid ultrasonic cleaners and harsh chemicals. Ruby, being exceptionally hard, is relatively resistant to damage but should still be cleaned gently with a soft brush and warm, soapy water.
Regular cleansing and energizing are recommended for all gemstones. Bathing them in full moonlight or placing them on a piece of selenite can help restore their energy. Removing jewelry daily to allow the stones to rest is also advised.
Conclusion
The December birthstones – turquoise, zircon, tanzanite, and historically, ruby – represent a rich tapestry of geological origins, historical significance, and cultural beliefs. From the ancient associations with ruby to the modern appeal of tanzanite, each gemstone offers a unique expression of December’s spirit. The diverse palette of blues, greens, and reds reflects the cool tones of winter and the warmth of year-end celebrations. Whether chosen for their aesthetic beauty, symbolic meaning, or perceived metaphysical properties, these gemstones continue to captivate and inspire.