December, the final month of the year, is unique in the birthstone calendar, as it is one of the two months with three recognized birthstones: turquoise, tanzanite, and zircon. This trio of gemstones, each with its own distinctive characteristics, origins, and symbolism, offers a fascinating study in the intersection of geology, history, and human culture. Whether you're drawn to the deep blue-green of turquoise, the velvety blue-violet of tanzanite, or the vibrant color versatility of zircon, December's birthstones present a rich tapestry of color and significance.
In this article, we will explore each of these gemstones in detail, examining their historical significance, geological formation, gemological properties, and cultural meanings. We will also provide practical advice on how to care for and appreciate these precious stones. Let’s begin our journey into the world of December’s birthstones.
Historical and Cultural Significance
Turquoise: A Gemstone of Antiquity
Turquoise is one of the oldest known gemstones, with a history that spans thousands of years and multiple civilizations. Its name comes from the French turquoise, meaning “Turkish,” as it was once believed to have originated in Turkey, although it is now known to have been sourced from regions like Iran, China, and the Americas.
As early as 3000 BCE, turquoise was highly valued in ancient Egypt, where it was used in jewelry and amulets. Pharaohs and high-ranking officials adorned themselves with turquoise to symbolize protection and divine favor. The Indus Valley Civilization also used turquoise in beads and ornaments.
In the United States, turquoise has long been a sacred stone among Native American tribes, particularly the Navajo and Zuni. It was often used in ceremonial jewelry and was believed to bring good fortune and spiritual protection.
Historically, turquoise was also significant in Persia (modern-day Iran) and China, where it was carved into intricate inlays and jewelry. In Persia, it was known as shahid, meaning “witness,” and was believed to alert the wearer to danger by cracking or changing color. In China, turquoise was used in jade-like carvings and was associated with wisdom and immortality.
Tanzanite: A Modern Marvel
In contrast to the ancient history of turquoise, tanzanite is a relatively new gemstone. Discovered in the Merelani Hills of Tanzania in the 1960s, tanzanite was first identified as zoisite in 1962. It wasn’t until 1967 that the gem was recognized for its unique blue-violet color, and by 1968, Tiffany & Co. had launched a major marketing campaign to promote it as a new luxury gemstone.
Tanzanite was officially added to the December birthstone list in 2002, becoming one of the most recent additions to the birthstone tradition. Its name is derived from its sole source of origin — Tanzania — and it is considered one of the rarest gemstones in the world. The gem’s velvety blue to violet hues, often with a purplish undertone, make it highly desirable in fine jewelry.
Due to its limited geographic origin, tanzanite is expected to become even more valuable in the future, especially as mining in the Merelani Hills becomes more difficult and less sustainable.
Zircon: The Many-Faced Stone
Zircon is a versatile gemstone that occurs in a wide range of colors, from deep red and golden yellow to colorless and blue. It has been used in jewelry for centuries and was even mistaken for diamonds in ancient times due to its brilliance and fire.
Historically, zircon was known in ancient Greece as the "hyacinth", a name derived from the myth of Hyacinthus, a young man transformed into a flower after his tragic death. This myth is often associated with rebirth, and in some cultures, zircon was believed to symbolize new beginnings and renewal.
Zircon was also popular in Victorian and Art Deco jewelry, where its bright color and durability made it a favorite for both ornamental and functional pieces. It is also known for its high refractive index, giving it a sparkling, diamond-like appearance when cut properly.
Zircon is particularly notable for its heat treatment, which is commonly used to enhance its color. The most popular color enhancement is blue zircon, which is achieved through controlled heating. This blue zircon is sometimes referred to as "star blue zircon" and is a popular alternative to more expensive blue gemstones like sapphire.
Geological Formation and Sources
Turquoise: A Product of Time and Chemistry
Turquoise is a phosphorus-based mineral with the chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O. It forms in anhydrous environments — typically in arid regions where copper-bearing minerals react with phosphoric acid, often in the presence of groundwater and alkaline conditions.
This reaction occurs in weathered copper deposits, often in limestone or sandstone. The presence of iron and aluminum in the surrounding rock influences the color of the turquoise, producing a range from deep blue to yellow-green. The matrix, or the veins of surrounding rock, often gives turquoise its characteristic patterns.
Major sources of turquoise include:
- Iran (historically known as Nishapur)
- Mexico
- United States (particularly Nevada and Arizona)
- China
- Russia
- Egypt (ancient sources)
Turquoise is a soft gemstone, rated 5 to 6 on the Mohs scale of hardness, and is relatively porous and fragile. This makes it sensitive to heat, chemicals, and physical damage, requiring careful handling and proper care to preserve its beauty.
Tanzanite: A Unique Geological Phenomenon
Tanzanite is a trigonal mineral with the chemical formula Ca₂Al₃(SiO₄)₃(OH). It is a trigonal zoisite that undergoes a heat treatment to enhance its color from a brownish green to a vibrant blue to violet. The gem is only found in the Merelani Hills of northern Tanzania, which is a geologically unique area.
The Merelani Hills are located near Mount Kilimanjaro, and the region is characterized by granitic rock formations and alkaline intrusions, which create the ideal conditions for tanzanite to form. The gemstone is typically found in metamorphic rocks, specifically in limestones and mica schists, where it forms under high-pressure and high-temperature conditions.
Mining in the Merelani Hills is labor-intensive, with many small-scale miners working in deep pits, often over 100 meters below the surface. The limited geographic source of tanzanite, combined with its increasingly difficult mining conditions, means that the gem is expected to become rare and valuable in the future.
Tanzanite is rated 6.5 to 7 on the Mohs scale, making it relatively durable, but it can still be susceptible to scratches and chipping if not handled carefully.
Zircon: A Versatile and Abundant Gem
Zircon is a zirconium silicate mineral with the chemical formula ZrSiO₄. It occurs naturally in a wide range of colors, including brown, red, yellow, green, blue, and colorless. The most popular and valuable form is blue zircon, which is created through heat treatment that stabilizes the color and enhances its brilliance.
Zircon is found in a variety of igneous and metamorphic rocks, and it is particularly common in granites, gneisses, and sedimentary deposits. The gem is often found as crystals or grains embedded in other rocks.
Key sources of zircon include:
- Sri Lanka
- Australia
- Myanmar
- Vietnam
- Cambodia
- Brazil
- India
- Madagascar
Zircon is rated 6 to 7.5 on the Mohs scale, making it fairly durable, but it can be brittle in certain cuts, particularly those with sharp angles or thin facets. Heat-treated zircon is also sensitive to light, with some stones reverting to their original color if exposed to prolonged sunlight.
Gemological Properties
| Property | Turquoise | Tanzanite | Zircon (Blue) |
|---|---|---|---|
| Chemical Formula | CuAl₆(PO₄)₄(OH)₈·4H₂O | Ca₂Al₃(SiO₄)₃(OH) | ZrSiO₄ |
| Color | Blue to green, often with matrix | Blue to violet, with purplish undertones | Blue (heat-treated) |
| Luster | Waxy to vitreous | Vitreous | Vitreous |
| Transparency | Opaque to semi-translucent | Transparent to translucent | Transparent |
| Hardness (Mohs) | 5–6 | 6.5–7 | 6–7.5 |
| Specific Gravity | 2.6–2.8 | 3.1–3.4 | 4.6–4.8 |
| Refractive Index | 1.61–1.65 | 1.69–1.73 | 1.92–2.00 |
| Cleavage | None (fragile) | Perfect cleavage in one direction | None or poor |
| Treatments | Stabilization (for hardness) | Heat treatment for color enhancement | Heat treatment for color enhancement |
| Origin | Iran, Mexico, U.S., China | Merelani Hills, Tanzania | Sri Lanka, Australia, Vietnam, etc. |
| Symbolism | Protection, health, prosperity | Rebirth, transformation, rarity | New beginnings, purity (white), prosperity |
Turquoise: A Stone of Protection and Prosperity
Turquoise is known for its soft, waxy luster and unique matrix patterns, which make each piece of turquoise jewelry one-of-a-kind. Its low hardness and porosity mean that it is best suited for low-impact jewelry, such as pendants and earrings, rather than rings or bracelets that may be exposed to frequent wear and tear.
The gem’s translucency and color variation are influenced by the concentration of copper and iron in its composition. The most prized turquoise is deep blue with minimal matrix, while matrix-heavy turquoise is often considered more ornamental than gem-quality.
Despite its softness, turquoise is often stabilized with resins or oils to improve its hardness and durability, making it more suitable for jewelry use. This process is considered standard in the industry and does not detract from the stone’s beauty or value.
Tanzanite: The Velvet Blue of Tanzania
Tanzanite is prized for its deep, velvety blue to violet color, which is caused by the presence of vanadium in its chemical structure. The gem is typically transparent to translucent and has a glassy luster that enhances its sparkling appearance.
One of the most notable features of tanzanite is its trichroism — the ability to display three different colors when viewed from different angles. This makes it a visually dynamic gemstone, and it is often cut in a way that maximizes the display of its color.
Tanzanite is also known for its large gemstone sizes, with large, high-quality stones being particularly valuable. The gem’s rarity and beauty have made it a popular choice for fine jewelry, especially in rings, pendants, and earrings.
Zircon: A Rainbow of Colors and Brilliance
Zircon is a highly refractive gemstone, which gives it a sparkling, almost diamond-like appearance when cut properly. The most popular and valuable form is blue zircon, which is created through heat treatment and is often used as a budget-friendly alternative to sapphire.
Zircon can be found in a wide range of colors, including:
- Blue (most popular)
- Yellow or golden (known as hessonite)
- Red or brown (often heat-treated to blue)
- Colorless (often mistaken for diamond)
- Green (rare)
Zircon is also known for its high dispersion, or fire, which gives it a rainbow-like sparkle when exposed to light. This makes it a popular choice for jewelry, particularly in vintage and Art Deco designs.
Symbolism and Metaphysical Beliefs
Turquoise: A Stone of Protection and Healing
Turquoise has long been associated with protection, healing, and good fortune. In ancient Egypt, it was believed to ward off evil spirits and was used in amulets and talismans for this purpose. In Native American cultures, turquoise was considered a spiritual stone, often used in ceremonial jewelry and medicine bags.
In Chinese culture, turquoise was associated with immortality and was used in imperial jewelry and funerary objects. In Persia, it was believed that turquoise would crack or change color if danger approached, acting as a warning sign.
Modern metaphysical beliefs continue to associate turquoise with calmness, clarity, and protection, making it a popular choice for meditation and healing practices.
Tanzanite: A Stone of Transformation and Rebirth
Tanzanite is often associated with transformation, intuition, and spiritual awakening. Its rarity and deep color are thought to represent inner strength and resilience, making it a symbol of personal growth and change.
In some metaphysical traditions, tanzanite is believed to enhance emotional clarity and help individuals release old patterns and embrace new beginnings. It is also thought to promote emotional healing and inner peace, making it a valuable tool for meditation and self-reflection.
Zircon: A Stone of New Beginnings and Prosperity
Zircon has long been associated with new beginnings, rebirth, and prosperity. In ancient Greece, it was linked to the myth of Hyacinth, a young man transformed into a flower after his tragic death, symbolizing renewal and transformation.
In modern metaphysical practices, zircon is believed to enhance creativity, stimulate the mind, and encourage personal growth. Blue zircon is particularly valued for its calming and soothing properties, while yellow zircon is associated with optimism and abundance.
Zircon is also considered a stone of the heart, helping to open emotional channels and foster compassion and understanding.
Care and Cleaning
Turquoise
Due to its low hardness and porosity, turquoise requires special care to maintain its beauty and durability.
- Avoid exposure to water, chemicals, and heat, as these can cause the stone to fade, crack, or lose its luster.
- Store turquoise separately from harder gemstones to prevent scratches.
- Clean with a soft cloth and mild soap in warm water. Ultrasonic and steam cleaners are not recommended, as they can damage the stone.
- If the stone is stabilized, it may be more resistant to damage, but it should still be treated with gentle care.
Tanzanite
Tanzanite is relatively durable, but it can still be susceptible to scratches and chipping, especially if it has cleavage planes.
- Avoid exposure to harsh chemicals and abrasives.
- Clean with a soft brush and mild soap in warm water.
- Avoid ultrasonic cleaners, as they can cause internal fractures.
- Avoid exposing tanzanite to extreme heat, as this can alter its color.
Zircon
Zircon, especially heat-treated blue zircon, should be handled with care to prevent color loss.
- Avoid prolonged exposure to bright light, as this can cause some zircons to revert to their original color.
- Avoid exposure to heat, as this can alter the color or structure of the stone.
- Clean with a soft brush and mild soap in warm water.
- Avoid ultrasonic and steam cleaners, as they can damage the stone.
Conclusion
December’s birthstones — turquoise, tanzanite, and zircon — offer a fascinating blend of historical significance, geological rarity, and symbolic meaning. From the ancient allure of turquoise to the modern marvel of tanzanite and the versatile brilliance of zircon, each gemstone represents a different aspect of human history and cultural expression.
Whether you are drawn to the deep blue-green of turquoise, the velvety blue-violet of tanzanite, or the sparkling rainbow of zircon, these gemstones offer something for every taste and occasion. As December is a time of change, reflection, and celebration, these birthstones serve as a beautiful reminder of the past, present, and future.
For those who were born in December, these stones are not just jewelry, but symbols of identity and connection to the world’s rich gemological and cultural heritage.