Introduction
December is unique in the world of birthstones, offering a wider array of gems than any other month. While the winter month is traditionally associated with a cool, blue palette, the specific stones recognized have evolved over centuries, influenced by ancient calendars, modern trade associations, and significant gemological discoveries. The primary December birthstones—turquoise, zircon, and tanzanite—are all celebrated for their captivating shades of blue, reflecting the frosty hues of the season. However, historical records and cultural traditions reveal a diverse list of stones, including blue topaz, lapis lazuli, and even red ruby and green chrysoprase, each carrying its own legacy. This article explores the rich history, geological origins, gemological properties, and symbolic meanings of December's birthstones, providing a comprehensive guide for enthusiasts, collectors, and anyone born in this festive month.
History and Lore: From Ancient Calendars to Modern Lists
The concept of birthstones is deeply rooted in history, with origins tracing back to ancient civilizations such as Egypt, Greece, and Rome, where gemstones were believed to possess mystical and healing properties. The most cited historical foundation is the biblical description of the High Priest's breastplate, which featured twelve gemstones representing the twelve tribes of Israel and the twelve months of the year. Over time, these stones were associated with specific months, forming the basis for modern birthstone lists.
For December, the historical record is particularly rich and varied. In the old Arabic, Hebrew, Italian, Roman, and Indian (Ayurvedic) calendars, ruby was the designated birthstone for December. Before this, ruby was also the zodiac stone for Capricorn, a sign that partially falls in December. In the Hindu calendar, topaz is listed as the December birthstone. The old Russian calendar associates chrysoprase, a green variety of chalcedony, with the month. The old Tibetan calendar names onyx, a banded chalcedony, as the December stone. Bloodstone (heliotrope), a green chalcedony with red inclusions, is a traditional December birthstone dating back to the 15th century.
The modern standardized lists began to take shape in the early 20th century. In 1912, the National Association of Jewelers in the United States created an unofficial list that combined historical customs with gemstones deemed practical for jewelry companies to sell. This list initially included lapis lazuli for December. In 1952, the Jewelry Industry Council of America updated the list, adding zircon to December’s offerings and replacing lapis lazuli. Tanzanite, a relatively recent discovery, was added to the modern U.S. birthstone list in 2002, though it was already recognized in Britain at the time. The American Gem Trade Association made a further update in February 2013, replacing lapis lazuli with zircon as the official December stone in the U.S. The reason for December having so many birthstones is not definitively known, but it is often attributed to a desire to offer more affordable options and to incorporate new gemstone discoveries and commercial offerings into the traditional framework.
Geological Formation and Sources
The diverse December birthstones originate from different geological environments and are mined across the globe.
Turquoise is one of the oldest known gemstones, with a history of use spanning thousands of years. It is an opaque mineral, a hydrous phosphate of copper and aluminum, formed in arid regions where acidic, copper-rich water percolates through aluminum-bearing rocks. Major sources include the southwestern United States (notably Arizona and New Mexico), Iran, China, and Egypt.
Zircon, one of the oldest minerals on Earth, is a silicate of zirconium. While it occurs in a rainbow of colors, the blue variety is the most popular for December. The blue color is typically achieved through heat treatment of brown zircon. Major sources for gem-quality zircon include Australia, Sri Lanka, Thailand, Cambodia, and the United States.
Tanzanite is a relative newcomer to the gem world. Discovered in 1967 in the Merelani Hills of Tanzania, it is named for its country of origin. It is a variety of the mineral zoisite, and its vivid blue-to-purple color is the result of vanadium impurities and subsequent heat treatment. Tanzania remains the primary, and essentially the only, source of tanzanite, making it exceptionally rare.
Blue Topaz is a transparent silicate mineral of aluminum and fluorine. Its blue color is almost always the result of irradiation and heat treatment applied to colorless or pale topaz. Major mining locations include Sri Lanka, Brazil, Mexico, Nigeria, and the United States (Texas). It is the official state gem of Texas.
Lapis Lazuli is an opaque, deep-blue rock composed mainly of the mineral lazurite, with calcite and pyrite. Historically, the finest material came from Afghanistan, with other sources in Chile and Russia.
Chrysoprase, a variety of chalcedony (a microcrystalline form of quartz), gets its apple-to deep-green color from nickel inclusions. It is found in Australia, Brazil, India, Madagascar, and the United States (notably Oregon and California).
Gemological Properties
The physical and optical properties of December's birthstones vary significantly, influencing their durability, appearance, and suitability for jewelry.
| Gemstone | Mineral Family | Color | Hardness (Mohs) | Transparency | Key Characteristics |
|---|---|---|---|---|---|
| Turquoise | Phosphate | Blue to green | 5 - 6 | Opaque | Often shows a "spiderweb" matrix; porous. |
| Zircon | Silicate | Blue (treated) | 6.5 - 7.5 | Transparent to translucent | High refractive index and brilliance; can be brittle. |
| Tanzanite | Zoisite | Blue to purple | 6.5 - 7 | Transparent | Strong trichroism (shows three colors); pleochroic. |
| Blue Topaz | Silicate | Blue (treated) | 8 | Transparent | Durable for daily wear; often available in large sizes. |
| Lapis Lazuli | Rock (Lazurite) | Deep blue | 5 - 5.5 | Opaque | Mottled with gold (pyrite) and white (calcite). |
| Chrysoprase | Chalcedony | Apple to deep green | 6.5 - 7 | Translucent to opaque | Even color is prized; can fade with prolonged sun exposure. |
| Ruby | Corundum | Red | 9 | Transparent | The red variety of corundum; extremely hard and durable. |
| Onyx | Chalcedony | Black (often) | 6.5 - 7 | Opaque | Banded variety of chalcedony; often used for cameos. |
| Bloodstone | Chalcedony | Green with red spots | 6.5 - 7 | Opaque | A green chalcedony with red inclusions of jasper. |
Durability and Wearability: For everyday jewelry, hardness and toughness are critical. Blue topaz (Mohs 8) is the most durable of the blue December stones, making it excellent for rings and bracelets. Zircon (Mohs 6.5-7.5) and tanzanite (Mohs 6.5-7) are also relatively hard but can be brittle, requiring careful setting and handling to avoid chipping. Turquoise (Mohs 5-6) and lapis lazuli (Mohs 5-5.5) are much softer and more porous, making them better suited for pendants and earrings rather than rings that experience daily impact. Chrysoprase (Mohs 6.5-7) is moderately durable but can be sensitive to heat and strong light.
Symbolism and Metaphysical Beliefs
Across cultures and centuries, December's birthstones have been imbued with a wide range of symbolic meanings and metaphysical properties.
- Turquoise: Historically, turquoise has been a stone of protection, said to ward off negative energy and bring good fortune. It is also believed to promote emotional balance, tranquility, and healing.
- Zircon: This gem is associated with clarity of thought, wisdom, and prosperity. It is believed to bring peace of mind and enhance spiritual growth.
- Tanzanite: As a modern discovery, tanzanite's symbolism is often linked to transformation, new beginnings, and spiritual awakening. It is also said to facilitate communication and higher consciousness.
- Blue Topaz: Believed to increase both physical and spiritual strength, blue topaz is also associated with calmness, clarity, and creative expression.
- Lapis Lazuli: A stone of truth and wisdom, lapis lazuli is thought to heighten awareness, expand perspective, and free the wearer from negativity. It has been used for centuries in jewelry and decorative arts.
- Chrysoprase: This green stone is believed to enhance emotional balance and prevent depression, promoting a sense of joy and forgiveness.
- Ruby: In ancient traditions, ruby was considered a stone of courage and strength, said to strengthen the mind and bestow vitality.
- Onyx: Often regarded as a grounding stone, onyx is believed to protect the wearer from negativity and enhance self-control.
- Bloodstone: This stone is traditionally associated with courage, physical strength, and vitality. It was historically used as a talisman for protection and healing.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of December's birthstones, particularly given their varying hardness and stability.
- Turquoise and Lapis Lazuli: Due to their porosity and softness, these stones should be cleaned with a soft, damp cloth and mild soap. Avoid harsh chemicals, ultrasonic cleaners, and prolonged exposure to water, lotions, and cosmetics, which can damage the surface or cause discoloration.
- Zircon, Tanzanite, Blue Topaz, Chrysoprase, and Bloodstone: These stones can generally be cleaned with warm water, a mild detergent, and a soft brush. They are more resilient than turquoise but should still be protected from sharp blows and extreme temperature changes. Tanzanite is particularly sensitive to thermal shock and should not be exposed to rapid temperature changes.
- Ruby and Onyx: As members of the corundum and chalcedony families, respectively, they are quite durable. They can be cleaned using standard methods, including warm soapy water and a soft brush. Ultrasonic cleaners are generally safe for ruby but should be used with caution for onyx if it has been dyed or treated.
For all gemstones, it is advisable to remove jewelry before engaging in activities that could subject it to impact or harsh chemicals. Storing stones separately in soft cloth pouches will prevent scratching.
Conclusion
December's birthstones offer a remarkable spectrum of choices, from the ancient allure of turquoise and lapis lazuli to the modern brilliance of tanzanite and blue topaz. While the month is predominantly associated with a blue palette, the historical and cultural records reveal a diverse heritage that includes ruby, chrysoprase, onyx, and bloodstone. This variety allows individuals born in December to select a gemstone that resonates with their personal style, budget, and connection to history or metaphysical beliefs. Whether chosen for its geological rarity, symbolic power, or simply its captivating color, each December birthstone carries a unique story of formation, tradition, and beauty, making it a fitting emblem for the final month of the year.