For those born on December 21, the birthstone selection reflects the rich diversity of gemstones associated with the final month of the year. While December is known for having three officially recognized birthstones—turquoise, tanzanite, and zircon, particularly blue zircon—the gemstone associated with December 21 is often linked to Capricorn, the zodiac sign covering December 22 to January 19. This connection, however, intersects with the broader December birthstone tradition and zodiacal astrological beliefs, creating a fascinating overlap of cultural, historical, and geological significance.
This article explores the December 21 birthstone by examining the three officially recognized December birthstones, as well as the zodiacal birthstone for Capricorn. It delves into their geological properties, historical and cultural significance, symbolism, and care instructions, drawing exclusively from the sources provided.
Introduction
The December 21 birthstone is not a single gemstone, but rather a set of options rooted in both the modern birthstone tradition and zodiacal astrological associations. While turquoise, tanzanite, and blue zircon are the official December birthstones, Capricorn—which begins on December 22—is also associated with its own set of zodiacal birthstones, including chalcedony and emerald. This dual tradition reflects the evolving nature of birthstone lists over time and the influence of astrological beliefs in shaping cultural perceptions of gemstones.
The gemstones linked to December 21 and the Capricorn zodiac are not only prized for their aesthetic beauty but also for their symbolic meanings and historical uses. From ancient civilizations to modern jewelers, these stones have been revered for their colors, rarity, and perceived metaphysical properties.
This article will explore each of these gemstones in detail, covering their origins, properties, symbolism, and care, with a focus on the gemstones most relevant to December 21. By examining these stones, we gain a deeper appreciation for the cultural and geological significance of the December 21 birthstone tradition.
History and Lore of the December 21 Birthstone
The history of the December 21 birthstone is closely tied to both the zodiacal and the modern birthstone traditions. These traditions have evolved over time, influenced by religious texts, cultural practices, and the availability of gemstones.
Zoisite and Tanzanite: A Modern Discovery
The most recent addition to the December birthstone list is tanzanite, a gemstone discovered in the 1960s near Mount Kilimanjaro in Tanzania. Tanzanite is a variety of the mineral zoisite that exhibits a striking blue to violet coloration. It was first marketed by Tiffany & Co. and quickly became a popular choice for jewelry. Due to its unique color and pleochroism (the ability to display different colors depending on the viewing angle), tanzanite is considered a modern gemstone with a strong appeal to contemporary jewelers and collectors.
Tanzanite is notable for its rarity, as it is only found in a small geographical area. This exclusivity has contributed to its value and has reinforced its status as a desirable December birthstone.
Turquoise: A Stone of Ancient Significance
Turquoise has a long and storied history, dating back to ancient civilizations such as Egypt, Persia, and the Americas. It was highly valued for its blue-green color, which was believed to have protective and healing properties. In ancient Egypt, turquoise was associated with Hathor, the goddess of love and fertility, and was often used in amulets and jewelry.
The Persian and Chinese cultures also held turquoise in high regard, using it in decorative arts and religious ceremonies. In the American Southwest, turquoise was a central element in the jewelry and ceremonial objects of the Navajo, Zuni, and Hopi peoples.
Zircon: An Ancient and Durable Gemstone
Zircon, particularly blue zircon, has been used as a gemstone for centuries. It is one of the oldest minerals on Earth, with some zircon crystals dating back 4.4 billion years. Blue zircon is typically produced through heat treatment, which enhances its color and clarity.
Zircon was historically confused with diamond and sapphire due to its brilliance and refractive properties. It was also known as the “gem of the future” for its ability to glow under ultraviolet light, a property known as fluorescence.
Zircon has been found in ancient jewelry from Egypt, Greece, and India, and was often used in signet rings and amulets. It is considered a zodiacal birthstone for Capricorn, reflecting its long-standing association with the zodiac signs of the past.
Geological Formation and Sources
Each of the gemstones associated with December 21 has distinct geological origins and mining locations. Understanding these characteristics helps to appreciate their rarity and value.
Tanzanite
Tanzanite is formed from the mineral zoisite, which is a calcium aluminum silicate. It is found only in a small area near Mount Kilimanjaro in Tanzania, making it one of the most geographically restricted gemstones in the world. The gemstone is typically heat-treated to enhance its color from a brownish or greenish hue to a vivid blue or violet.
Tanzanite is relatively soft, with a Mohs hardness of 6 to 6.5, which means it requires careful handling and cleaning.
Turquoise
Turquoise is a phosphate mineral composed of copper and aluminum. It forms in the weathering zones of copper deposits and is often found in limestone or sandstone. Major sources include Iran, China, the United States, and Mexico.
Turquoise is typically opaque, with a waxy luster, and is known for its wide range of colors, from sky blue to greenish-blue. It is often enhanced with stabilization treatments to improve its durability and color.
Blue Zircon
Zircon is a zirconium silicate and is found in a variety of colors, including brown, red, yellow, and colorless. The blue variety is produced through heat treatment, which removes the brown color and enhances the blue hue.
Zircon is found in sedimentary rocks and is often mined as a byproduct of other mineral extraction. Major sources include Australia, Brazil, India, and Vietnam.
Zircon has a high refractive index and a Mohs hardness of 6.5 to 7.5, making it relatively durable for a gemstone. It is also fluorescent, which means it can glow under ultraviolet light.
Gemological Properties
The gemological properties of the December 21 birthstones are diverse, reflecting their different compositions and origins.
| Gemstone | Chemical Composition | Color Range | Hardness (Mohs Scale) | Transparency | Specific Gravity | Refractive Index |
|---|---|---|---|---|---|---|
| Tanzanite | Ca₂Al₃(SiO₄)₃(OH) | Blue, purple, violet | 6–6.5 | Transparent | 3.1–3.4 | 1.69–1.72 |
| Turquoise | CuAl₆(PO₄)₄(OH)₈·4H₂O | Blue, green, green-blue | 5–6 | Opaque | 2.6–2.8 | 1.61–1.65 |
| Blue Zircon | ZrSiO₄ | Blue, violet, blue-violet | 6.5–7.5 | Transparent | 4.6–4.7 | 1.92–2.01 |
Tanzanite
- Color: Tanzanite exhibits pleochroism, displaying different colors depending on the viewing angle. It is typically blue to violet when heat-treated.
- Hardness: 6–6.5 on the Mohs scale, making it relatively soft compared to other gemstones.
- Clarity: Tanzanite is often included due to its cotton-like inclusions, which are considered characteristic of the gem.
- Cut: Tanzanite is commonly cut in emerald or oval cuts to enhance its color and brilliance.
Turquoise
- Color: Turquoise ranges from sky blue to greenish-blue, depending on the amount of copper and aluminum in the stone.
- Hardness: 5–6 on the Mohs scale, making it relatively soft and prone to scratching.
- Clarity: Turquoise is typically opaque, with a waxy or greasy luster.
- Cut: Turquoise is often cabochon-cut to emphasize its chatoyancy and color.
Blue Zircon
- Color: Blue zircon is a deep blue or blue-violet after heat treatment.
- Hardness: 6.5–7.5 on the Mohs scale, making it relatively durable.
- Clarity: Zircon is usually clear or slightly included.
- Cut: Blue zircon is often cut in brilliant or step cuts to enhance its fire and brilliance.
Symbolism and Metaphysical Beliefs
The gemstones associated with December 21 carry rich symbolic and metaphysical meanings, rooted in both historical and zodiacal traditions.
Tanzanite
Tanzanite is believed to promote emotional healing, spiritual growth, and mental clarity. It is considered a stone of transformation, helping individuals embrace change and new beginnings. In spiritual practices, tanzanite is used to enhance intuition and inner vision.
Turquoise
Turquoise is one of the most spiritually significant gemstones in history. It is associated with protection, good fortune, and healing. In ancient Egypt, turquoise was believed to ward off evil spirits and was often used in amulets and jewelry. In the American Southwest, it was considered a stone of power and was used in ceremonial objects.
Turquoise is also associated with communication and expression, making it a popular stone for those in creative or public-facing professions.
Blue Zircon
Blue zircon is considered a stone of hope, optimism, and renewal. It is believed to enhance one’s ability to see the future and to embrace change with confidence. Blue zircon is also associated with wisdom, knowledge, and insight, making it a valuable stone for scholars and thinkers.
In ancient cultures, zircon was used in signet rings and amulets, and was believed to protect the wearer from harm and bring good luck.
Care and Cleaning
Due to their varying hardness and durability, the December 21 birthstones require different care and cleaning methods to maintain their beauty and integrity.
Tanzanite
Tanzanite is relatively soft, with a Mohs hardness of 6–6.5, and can be easily scratched or damaged. It is also sensitive to heat and sunlight, which can cause fading over time. Tanzanite should be stored separately from other gemstones to prevent scratches.
To clean tanzanite, use mild soap, warm water, and a soft brush. Avoid using ultrasonic or steam cleaners, as these can damage the gemstone.
Turquoise
Turquoise is very porous and can be easily damaged by water, oils, and chemicals. It should be stored in a dry, cool place and avoided contact with moisture. If turquoise becomes dry or cracked, it can be rehydrated by placing it in a sealed container with a damp cloth.
To clean turquoise, use a soft cloth and warm, soapy water. Avoid using abrasive materials or harsh chemicals.
Blue Zircon
Blue zircon is more durable than tanzanite or turquoise, with a Mohs hardness of 6.5–7.5. It is relatively resistant to scratches and heat, making it suitable for everyday wear.
To clean blue zircon, use mild soap, warm water, and a soft brush. It can also be cleaned with ultrasonic or steam cleaners, although it is best to consult a jeweler before using these methods.
Conclusion
The December 21 birthstone is a unique and multifaceted gemstone, reflecting the rich diversity of December's official and zodiacal birthstones. Whether you choose tanzanite, turquoise, blue zircon, or chalcedony, each of these gemstones carries its own historical significance, geological properties, and symbolic meaning.
From the rare and modern tanzanite to the ancient and spiritually significant turquoise, these stones offer a wide range of colors, textures, and energies that can resonate with the individual born on December 21. Whether you are drawn to the brilliance of zircon, the healing properties of turquoise, or the transformative power of tanzanite, these gemstones make for a meaningful and beautiful choice.
By understanding their history, properties, and care, you can ensure that your December 21 birthstone remains a valuable and cherished part of your life for years to come.