December is a month rich in cultural and symbolic significance, and its association with birthstones adds a layer of historical and gemological intrigue. Unlike many months that are typically assigned a single birthstone, December is uniquely represented by a collection of gemstones: Zircon, Turquoise, Opal, Garnet, Ruby, and, in more modern classifications, Tanzanite. These stones are not only diverse in their appearance and properties but also in their histories and cultural meanings. This article delves into the gemological properties, historical lore, and cultural significance of each of these December birthstones, drawing from cross-referenced sources to provide an authoritative and comprehensive overview.
Introduction
December’s birthstones reflect the diversity of the month itself—ranging from the fiery reds of garnet and ruby to the iridescent play of color in opal, and the cool blues of zircon and turquoise. The multiplicity of December’s birthstones can be traced back to historical traditions and evolving gemological practices. While the exact origins of birthstone associations are often shrouded in antiquity, the modern list of December birthstones was standardized in the early 20th century. Over time, additional gemstones such as tanzanite have been added, reflecting both scientific discoveries and the growing appreciation for rare and beautiful stones.
This article explores the key gemstones associated with December, examining their geological formation, cultural symbolism, and gemological properties. Each stone tells a unique story, rooted in history and science, and continues to captivate jewelers, collectors, and gem enthusiasts today.
History and Lore
The tradition of associating gemstones with specific months and zodiac signs is ancient, with roots in various cultures. One of the earliest known references to birthstones is found in the Breastplate of Aaron, described in the Book of Exodus in the Hebrew Bible. This artifact, worn by the high priest, is said to have contained twelve gemstones representing the twelve tribes of Israel. While the exact identification of these stones remains debated, the idea that gemstones could symbolize different groups and times has persisted through history.
In medieval Europe, the belief that gemstones possessed healing and protective properties became widespread. These beliefs were often tied to astrology and the idea that each stone was connected to a specific celestial body or zodiac sign. By the 19th and early 20th centuries, the concept of birthstones had evolved into a more structured system, with lists of stones for each month being formalized in gemological literature and jewelry trade publications.
For December, the selection of gemstones reflects both the historical significance of certain stones and their geological rarity and beauty. Zircon and turquoise, for instance, have long been valued in different cultures for their color and perceived mystical properties. Opal, with its iridescent play of color, has captivated many, while garnet and ruby, both red gemstones, have been associated with passion and vitality.
Modern additions such as tanzanite, discovered in the 1960s in Tanzania, highlight how the list of December birthstones continues to evolve with new discoveries and shifting trends in the gem trade. These additions are often influenced by marketing efforts from the jewelry industry, aiming to promote rarer and more unique stones.
Geological Formation and Sources
Each of December’s birthstones has a distinct geological origin and is formed under specific conditions. Understanding these processes helps explain the unique properties and characteristics of each gemstone.
Zircon
Zircon is a mineral composed of zirconium silicate and is found in a variety of colors, including yellow, green, red, brown, and blue. The blue zircon, in particular, is a popular variant and is formed when natural zircon is heat-treated. Zircon is typically found in metamorphic and igneous rocks, and major sources include Australia, India, Brazil, and Thailand.
Zircon is known for its high refractive index and dispersion, giving it a brilliance similar to diamond. Its hardness on the Mohs scale ranges from 6 to 7.5, making it relatively durable for use in jewelry, though it can be susceptible to chipping if mishandled.
Turquoise
Turquoise is a hydrated phosphate of aluminum and copper. It is typically found in arid regions, where it forms through the oxidation of copper minerals in the presence of water. The blue to green color of turquoise is due to the presence of copper. Major sources of turquoise include the United States (particularly Nevada and Arizona), China, Iran, and Egypt.
Turquoise is relatively soft, with a hardness of 5 to 6 on the Mohs scale. It is also porous and can absorb oils and dirt easily, which requires careful cleaning and maintenance. Historically, turquoise has been highly valued by Native American, Persian, and Egyptian cultures, often used in ceremonial and decorative items.
Opal
Opal is a hydrated amorphous form of silica and is known for its unique play of color, which results from the diffraction of light through microscopic silica spheres. Unlike most other gemstones, opal does not have a crystalline structure, which makes it unique in the gemological world. Opal is found in various locations around the world, including Australia (which produces the majority of the world’s opal), Mexico, Brazil, and Ethiopia.
Opal is quite soft, with a hardness of 5 to 6.5 on the Mohs scale, and it is also sensitive to changes in temperature and humidity. It is easily damaged and requires special care to maintain its luster and structural integrity.
Garnet
Garnet is not a single mineral but a group of minerals that share similar physical and chemical properties. The most common types of garnet include almandine, pyrope, and grossular. Garnet is typically found in metamorphic rocks such as schist and gneiss. Major sources include India, Sri Lanka, the United States, and Africa.
Garnet is relatively hard, with a hardness of 6.5 to 7.5 on the Mohs scale, making it suitable for use in jewelry. It is known for its rich red color, though it can also occur in green, yellow, and orange. Historically, garnet has been associated with protection and vitality.
Ruby
Ruby is a variety of the mineral corundum and is distinguished by its red color, which is caused by the presence of chromium. Ruby is formed under high-pressure and high-temperature conditions in igneous and metamorphic rocks. Major sources of ruby include Myanmar (Burma), Thailand, Sri Lanka, and Madagascar.
Ruby is one of the hardest gemstones, with a hardness of 9 on the Mohs scale. It is highly prized for its color and durability, making it a popular choice for high-quality jewelry. Ruby has been associated with power, passion, and vitality in various cultures throughout history.
Tanzanite
Tanzanite is a relatively recent addition to the list of December birthstones. It was discovered in the 1960s in Tanzania and is a variety of the mineral zoisite. Tanzanite is known for its striking blue to violet color, which is caused by the presence of vanadium. It is formed in metamorphic rocks under specific conditions.
Tanzanite has a hardness of 6 to 7 on the Mohs scale and is relatively durable for use in jewelry. It is a rare gemstone and is only found in Tanzania, making it a highly valuable and sought-after stone. Tanzanite was added to the list of December birthstones in the 1980s to promote the stone and increase its popularity.
Gemological Properties
Each of December’s birthstones has distinct gemological properties that influence its use in jewelry and its appeal to collectors. These properties include color, clarity, hardness, and refractive index.
Color
Color is one of the most important factors in determining the value and desirability of a gemstone. Each December birthstone has a unique color profile:
- Zircon: Available in a wide range of colors, including blue, yellow, green, and red. The blue zircon is particularly popular for its vibrant color and brilliance.
- Turquoise: Known for its blue to green color, which can vary in intensity depending on the presence of copper and other minerals.
- Opal: Famous for its play of color, which is caused by the diffraction of light through microscopic silica spheres. Opal can display a wide range of colors, from red and green to blue and violet.
- Garnet: Typically found in red, though it can also occur in green, yellow, and orange. The deep red color of garnet is highly prized.
- Ruby: Known for its rich red color, which can range from pink to blood-red. The color of ruby is caused by the presence of chromium.
- Tanzanite: Known for its striking blue to violet color, which is caused by the presence of vanadium. Tanzanite can display a range of colors depending on the lighting conditions.
Clarity
Clarity refers to the presence of inclusions or imperfections within a gemstone. The clarity of each December birthstone can vary depending on its origin and the conditions under which it was formed:
- Zircon: Often has inclusions, but these can be hidden by the stone’s brilliance and dispersion. High-quality zircon is relatively free of visible inclusions.
- Turquoise: Typically has inclusions and matrix patterns, which are considered part of the stone’s character. High-quality turquoise has a smooth, even color and minimal inclusions.
- Opal: Can be porous and may have inclusions or bubbles. The presence of play of color is more important than clarity in determining the value of opal.
- Garnet: Often has inclusions, but these are usually not visible to the naked eye. High-quality garnet is relatively free of visible inclusions.
- Ruby: Known for its clarity, with high-quality ruby having minimal inclusions. Inclusions in ruby are often considered part of the stone’s character and can be used to determine its origin.
- Tanzanite: Often has inclusions, but these are usually not visible to the naked eye. High-quality tanzanite is relatively free of visible inclusions.
Hardness
Hardness is measured on the Mohs scale, which ranges from 1 (talc) to 10 (diamond). The hardness of a gemstone determines its durability and suitability for use in jewelry:
| Gemstone | Hardness (Mohs Scale) |
|---|---|
| Zircon | 6–7.5 |
| Turquoise | 5–6 |
| Opal | 5–6.5 |
| Garnet | 6.5–7.5 |
| Ruby | 9 |
| Tanzanite | 6–7 |
Ruby is the hardest of the December birthstones, with a hardness of 9, making it highly durable. Opal and turquoise, on the other hand, are relatively soft and require special care to avoid damage.
Refractive Index
The refractive index of a gemstone determines how light is bent as it passes through the stone, affecting its brilliance and sparkle:
- Zircon: Has a high refractive index and dispersion, giving it a brilliance similar to diamond.
- Turquoise: Has a relatively low refractive index and is not as brilliant as other gemstones.
- Opal: Has a unique play of color caused by the diffraction of light through microscopic silica spheres.
- Garnet: Has a moderate refractive index and is known for its brilliance and fire.
- Ruby: Has a high refractive index and is known for its brilliance and fire.
- Tanzanite: Has a moderate refractive index and is known for its brilliance and color.
Symbolism and Metaphysical Beliefs
Throughout history, gemstones have been attributed with various symbolic and metaphysical properties. These beliefs vary across cultures and time periods, but they often reflect the characteristics and colors of the stones.
Zircon
Zircon has been associated with wisdom, clarity, and spiritual insight. It is believed to enhance one’s ability to see the truth and to promote emotional balance. In some cultures, zircon is used in meditation to help calm the mind and enhance spiritual awareness.
Turquoise
Turquoise has long been associated with protection, healing, and good fortune. In Native American cultures, turquoise is considered a sacred stone and is used in ceremonies and rituals. It is believed to promote health, happiness, and spiritual connection. In ancient Egypt, turquoise was used in jewelry and amulets to protect the wearer from harm.
Opal
Opal is often associated with creativity, intuition, and emotional sensitivity. It is believed to enhance artistic expression and to help individuals connect with their inner emotions. Opal is also associated with love and passion, making it a popular choice for romantic gifts.
Garnet
Garnet is associated with protection, vitality, and energy. It is believed to promote strength and courage and to help individuals overcome challenges. In some cultures, garnet is used to ward off negative energy and to promote positive relationships.
Ruby
Ruby is associated with passion, power, and vitality. It is believed to enhance one’s courage and to help individuals achieve their goals. Ruby is also associated with love and is often used in engagement rings and other romantic jewelry.
Tanzanite
Tanzanite is associated with transformation, intuition, and spiritual growth. It is believed to help individuals release old patterns and to embrace new beginnings. Tanzanite is also associated with balance and harmony, making it a popular choice for those seeking emotional and spiritual stability.
Care and Cleaning
Proper care and cleaning are essential for maintaining the beauty and longevity of December’s birthstones. Each stone has specific requirements due to its hardness, porosity, and sensitivity to environmental factors.
Zircon
Zircon is relatively durable but can be susceptible to chipping. It should be cleaned with mild soap and warm water. Avoid using harsh chemicals or ultrasonic cleaners, as these can damage the stone. Store zircon separately from other gemstones to prevent scratches.
Turquoise
Turquoise is relatively soft and porous, making it sensitive to oils, dirt, and changes in humidity. It should be cleaned with a soft cloth and mild soap. Avoid using ultrasonic cleaners or steamers, as these can damage the stone. Store turquoise in a cool, dry place to prevent discoloration.
Opal
Opal is sensitive to changes in temperature and humidity. It should be kept in a stable environment and cleaned with a soft cloth and mild soap. Avoid exposing opal to direct sunlight or extreme temperatures, as this can cause it to crack or lose its luster.
Garnet
Garnet is relatively durable and can be cleaned with mild soap and warm water. It can also be cleaned with ultrasonic or steam cleaners. Store garnet separately from other gemstones to prevent scratches.
Ruby
Ruby is one of the hardest gemstones and can be cleaned with mild soap and warm water. It can also be cleaned with ultrasonic or steam cleaners. Store ruby separately from other gemstones to prevent scratches.
Tanzanite
Tanzanite is relatively durable but can be sensitive to high heat and strong light. It should be cleaned with mild soap and warm water. Avoid using ultrasonic or steam cleaners, as these can damage the stone. Store tanzanite in a cool, dry place to prevent discoloration.
Conclusion
December’s birthstones represent a fascinating array of colors, properties, and cultural significance. From the brilliant blue of zircon to the iridescent play of color in opal, each stone has its own unique charm and history. These gemstones have been valued for centuries for their beauty, rarity, and symbolic meanings, and they continue to captivate jewelers, collectors, and gem enthusiasts today. Understanding the geological properties, historical lore, and care requirements of these stones allows us to appreciate their beauty and significance even more. Whether worn as jewelry or studied as part of gemology, December’s birthstones offer a rich and rewarding subject for exploration.