December, the last month of the Gregorian calendar, is associated with a rich and complex history of birthstones. Unlike most months, which are typically assigned a single birthstone, December has had the most dramatic and evolving list of gemstone designations. This month has been linked to several different stones across various historical periods, from ancient civilizations to modern jewelry industry standards. Understanding the origins of December’s birthstones provides insight into how gemstones have been valued, traded, and symbolized through time.
This article delves into the historical, cultural, and gemological aspects of December’s birthstones, focusing on the original stone and the modern designations that have followed. By examining the sources available, we can uncover the reasons behind the changes in December’s birthstone list and how these gemstones reflect both the science of mineralogy and the lore of cultural traditions.
Historical and Cultural Significance
The concept of birthstones is deeply rooted in ancient traditions, particularly in biblical and cultural references. The earliest known birthstone lists are found in the Bible, specifically in the Book of Exodus and the Book of Revelation, which describe the 12 stones on Aaron’s breastplate and the 12 foundation stones of the New Jerusalem. These stones were believed to represent the 12 tribes of Israel and the 12 zodiac signs, respectively.
For December, the original birthstone appears to have been heliodor, a greenish-yellow variety of beryl. In the Book of Revelation 21:19-20, the tenth foundation stone is described as heliodor, which was associated with the zodiac sign Capricorn and the month of December. However, this association is not entirely straightforward. Ancient texts often used different terms for the same gemstone or described different stones for the same purpose, leading to confusion over time.
One of the key historical challenges in identifying December’s original birthstone is the ambiguity in the description of the stone called chrysoprase in ancient texts. While many modern interpretations refer to chrysoprase as a green variety of chalcedony, historical accounts suggest that the original chrysoprase may have been a golden-colored beryl, which aligns more closely with heliodor. This distinction is critical in understanding the early designation of December’s birthstone.
In several ancient cultures, including those in India, December was associated with ruby. Ruby, the red variety of corundum, was revered as the gemstone of the Sun and was considered to be one of the most powerful stones in the zodiac. In India, ruby was linked to both July and December, a dual association that reflects the complex and sometimes overlapping systems of gemstone symbolism in different parts of the world.
By the 14th to 19th centuries, the European understanding of December’s birthstone had shifted. Ruby remained a popular choice, especially in countries like Poland, Russia, and Spain, where it was seen as the December birthstone. However, in 1912, the Jewelers of America reorganized the birthstone calendar, moving ruby to July and assigning December to turquoise. This marked a significant turning point in the modern birthstone system.
Turquoise, a gemstone native to Iran, became the official December birthstone in the United States in the early 20th century. Its blue-green color and historical significance in various cultures made it an ideal choice for the month of December, especially as it complemented the winter season and the symbolism of change and renewal.
The modern list of December birthstones has continued to evolve. In 1953, blue zircon was added to the list, and in 2002, tanzanite was introduced as the newest official December birthstone by the Jewelers of America. These additions reflect the growing diversity of gemstone choices and the increasing recognition of rare and unique stones in the jewelry industry.
Despite these additions, the original December birthstone—heliodor—remains an important part of the historical narrative. The shift from heliodor to turquoise, and later to zircon and tanzanite, illustrates how the birthstone system has adapted to cultural, economic, and scientific influences over time.
Geological Formation and Sources
Each of December’s birthstones has a unique geological origin and set of properties that define its formation and availability. Understanding the geological context of these gemstones provides insight into why certain stones were chosen for specific months and how their availability has influenced their popularity.
Heliodor
Heliodor is a yellow to yellow-green variety of beryl. Beryl is a beryllium aluminum silicate (Be₃Al₂(SiO₃)₆) that forms in granitic pegmatites—rock formations that are rich in rare elements and often contain other gemstones like emerald and aquamarine. Heliodor is typically found in Brazil, Madagascar, and the United States. Its yellow color is due to trace amounts of iron in the crystal structure.
The historical association of heliodor with December is based on its description in the Book of Revelation. However, the stone was not widely traded or used in jewelry during ancient times, which may have contributed to its replacement by other gemstones in later centuries.
Turquoise
Turquoise is a hydrated phosphate of aluminum and copper, with the chemical formula Al₂(OH)₃PO₄·nH₂O. It forms in the oxidation zones of copper deposits, typically in arid environments where water has percolated through the rock and deposited copper and aluminum. The most famous sources of turquoise include Iran, China, Egypt, and the southwestern United States.
Turquoise has been mined and used for thousands of years, with evidence of its use dating back to ancient Egypt. Its blue-green color is due to the presence of copper, and the presence of other minerals such as iron and aluminum can affect the shade and pattern of the stone.
Turquoise was added to the official birthstone list in 1912, and its popularity has remained strong due to its availability and aesthetic appeal. It is commonly used in jewelry, especially in Native American and Middle Eastern designs.
Blue Zircon
Zircon is a silicate mineral with the formula ZrSiO₄. It is one of the oldest minerals on Earth, with some zircon crystals dating back over 4 billion years. Blue zircon, in particular, is a popular gemstone due to its vibrant blue color and high refractive index, which gives it a brilliant sparkle.
Blue zircon is created through heat treatment, which alters the color of the stone from brown to blue. It is found in various parts of the world, including Australia, Thailand, and Cambodia. Blue zircon was added to the December birthstone list in 1953, and its inclusion reflects the growing appreciation for heat-treated gemstones in the mid-20th century.
Tanzanite
Tanzanite is a blue-violet variety of the mineral zoisite. It has the chemical formula Ca₂Al₃(SiO₄)(Si₂O₇)O(OH). Tanzanite is a pleochroic gemstone, meaning it can display different colors depending on the angle from which it is viewed. It is found only in one location in the world: the foothills of Mount Kilimanjaro in northern Tanzania. This limited source makes tanzanite one of the rarest gemstones in the world.
Tanzanite was discovered in 1967 and added to the December birthstone list in 2002. Its inclusion highlights the importance of rare and unique gemstones in the modern jewelry industry. Due to its limited availability, tanzanite is considered a luxury gemstone and is often used in high-end jewelry pieces.
Gemological Properties
Each of December’s birthstones has distinct gemological properties that make them unique and suitable for different types of jewelry. These properties include hardness, refractive index, color, and other physical characteristics that influence their durability and appearance.
| Gemstone | Hardness (Mohs Scale) | Refractive Index | Color | Chemical Formula | Common Sources |
|---|---|---|---|---|---|
| Heliodor | 7.5–8 | 1.56–1.60 | Yellow to yellow-green | Be₃Al₂(SiO₃)₆ | Brazil, Madagascar, USA |
| Turquoise | 5–6 | 1.61–1.65 | Blue-green | Al₂(OH)₃PO₄·nH₂O | Iran, China, USA |
| Blue Zircon | 6–7.5 | 1.92–2.01 | Blue | ZrSiO₄ | Australia, Thailand, Cambodia |
| Tanzanite | 6–7 | 1.694–1.701 | Blue-violet | Ca₂Al₃(SiO₄)(Si₂O₇)O(OH) | Tanzania |
Heliodor
Heliodor is relatively hard, with a Mohs hardness of 7.5–8, making it suitable for use in jewelry. Its refractive index ranges from 1.56 to 1.60, which gives it a moderate brilliance. Due to its hardness and stability, heliodor can be cut into various shapes and polished to a high luster.
Turquoise
Turquoise is a softer gemstone, with a hardness of 5–6 on the Mohs scale. It is more susceptible to scratches and damage, so it requires careful handling. Its refractive index ranges from 1.61 to 1.65, which is relatively low compared to other gemstones. Turquoise is often stabilized or treated with resins to improve its durability and appearance.
Blue Zircon
Blue zircon has a hardness of 6–7.5, which makes it suitable for use in jewelry, although it is not as durable as harder gemstones like diamonds or sapphires. Its high refractive index (1.92–2.01) gives it a brilliant sparkle and fire, making it a popular choice for rings and pendants.
Tanzanite
Tanzanite has a hardness of 6–7 on the Mohs scale, which is relatively moderate. Its high refractive index (1.694–1.701) and pleochroic nature make it a visually striking gemstone. Due to its rarity and beauty, tanzanite is often used in fine jewelry and is considered a luxury gemstone.
Symbolism and Metaphysical Beliefs
Throughout history, gemstones have been attributed with symbolic and metaphysical properties. These beliefs vary across cultures and time periods, but they often reflect the values and traditions of the societies that valued these stones.
Heliodor
Heliodor has been associated with clarity of thought, emotional balance, and spiritual growth. In ancient times, it was believed to bring good fortune and protection from negative energy. Its golden-yellow color was seen as a symbol of joy and optimism.
Turquoise
Turquoise has long been associated with protection, healing, and wisdom. In ancient Egypt, it was used in burial masks and amulets to protect the dead in the afterlife. Native American cultures have used turquoise in jewelry and rituals to promote spiritual connection and healing. In modern times, turquoise is believed to enhance communication, attract prosperity, and bring emotional stability.
Blue Zircon
Blue zircon is often associated with love, loyalty, and emotional healing. It is believed to promote inner peace and clarity of thought. In ancient times, zircon was considered a stone of wisdom and was used in divination and spiritual practices.
Tanzanite
Tanzanite is associated with transformation, intuition, and emotional balance. Its pleochroic nature is seen as a symbol of change and adaptability. Tanzanite is believed to help individuals connect with their inner selves and gain insight into their emotional and spiritual states.
Care and Cleaning
Due to their varying hardness and chemical properties, the different December birthstones require different care and cleaning methods to maintain their beauty and durability.
Heliodor
Heliodor is relatively durable, with a hardness of 7.5–8 on the Mohs scale. It can be cleaned with warm soapy water and a soft cloth. Avoid using ultrasonic or steam cleaners, as these can cause damage. Store heliodor away from harder gemstones to prevent scratches.
Turquoise
Turquoise is a softer gemstone with a hardness of 5–6. It is sensitive to heat, chemicals, and moisture, so it should be cleaned gently with a soft cloth and mild soap. Avoid exposure to strong chemicals, as they can cause discoloration or damage. Store turquoise in a dry, cool place away from direct sunlight.
Blue Zircon
Blue zircon has a hardness of 6–7.5 and can be cleaned with warm soapy water and a soft cloth. Avoid using ultrasonic or steam cleaners, as these can cause damage. Store blue zircon away from harder gemstones to prevent scratches.
Tanzanite
Tanzanite has a hardness of 6–7 and is relatively durable. It can be cleaned with warm soapy water and a soft cloth. Avoid using ultrasonic or steam cleaners, as these can cause damage. Store tanzanite away from harder gemstones to prevent scratches.
Conclusion
The history of December’s birthstone is a fascinating journey through time, reflecting the changing values, beliefs, and practices of different cultures. From the original designation of heliodor in ancient texts to the modern inclusion of turquoise, zircon, and tanzanite, the evolution of December’s birthstones illustrates how gemstones have been valued and utilized throughout history.
Each of these gemstones has unique geological properties, cultural significance, and symbolic meanings. Whether used in jewelry, for spiritual purposes, or as a symbol of personal identity, these stones continue to captivate and inspire.
Understanding the origins and evolution of December’s birthstones provides a deeper appreciation for the role that gemstones play in our lives. As new discoveries and trends emerge, the story of December’s birthstones will undoubtedly continue to evolve, reflecting the ever-changing world of gemology and jewelry.