December is unique among the months, boasting not one, but four recognized birthstones: Tanzanite, Turquoise, Blue Zircon, and Blue Topaz. All four gems share a common thread – a beautiful spectrum of blue hues – reflecting the cool tones of the winter season. This article will delve into the history, geological origins, gemological properties, and symbolism of these captivating December birthstones, providing a comprehensive overview for enthusiasts and those seeking to understand their significance.
A History of December’s Gems
The association of specific gemstones with months of the year dates back to ancient times, initially linked to the zodiac. While early traditions often assigned a single stone per month, the modern practice of multiple birthstones gained traction in the 20th century, offering greater choice and reflecting the diversity of available gems. Turquoise has the longest history of use among these December stones, cherished for millennia by cultures across the globe. As early as 3000 years ago, Chinese artisans carved turquoise, and the pharaohs of ancient Egypt adorned themselves with it, believing it possessed protective and beneficial powers. The name “turquoise” itself originates from the French “pierre tourques,” meaning “Turkish stone,” reflecting its passage to Europe through Turkish trade routes in the 13th century. Historically, the most prized turquoise came from Persia (modern-day Iran), known as “Persian blue,” a designation still used even for turquoise found elsewhere. The Sinai Peninsula in Egypt also served as an ancient source, with the gem integrated into religious and cultural artifacts.
Blue Zircon, while less steeped in ancient lore than turquoise, has a history stretching back centuries. Its varied colors have led to multiple trade names throughout history, including “hyacinth” for reddish-brown varieties and “jargon” for lighter yellows. Tanzanite is the newest addition to the December birthstone family, discovered in Tanzania in 1967. Its relatively recent discovery means it lacks the extensive historical background of turquoise or zircon, but its captivating color quickly established its popularity. Blue Topaz, while also a December birthstone, is not extensively detailed within the provided sources.
Geological Formation and Sources
The geological origins of these birthstones are as diverse as their appearances. Turquoise is a hydrated phosphate of copper and aluminum, forming in relatively dry, arid environments. It typically occurs as a secondary mineral in volcanic rocks, forming within veins and cavities. The presence of iron and other trace elements contributes to the variations in its color, ranging from sky blue to greenish-blue.
Zircon forms in igneous rocks and metamorphic rocks, often as a byproduct of magma crystallization. It is a zirconium silicate (ZrSiO4) and can be found in a wide range of colors, though blue zircon is often achieved through heat treatment. The sources of zircon are widespread, with deposits found in various locations globally.
Tanzanite, a relatively recent discovery, is a blue to violet-violet variety of the mineral zoisite. It is found in a very limited geographical area: the Merelani Hills of northern Tanzania. This restricted source contributes to its rarity and value. The formation of tanzanite is linked to the complex geological processes associated with the Pan-African orogeny, a period of mountain building that occurred hundreds of millions of years ago.
Gemological Properties
Each of these December birthstones possesses unique gemological properties that contribute to its beauty and desirability.
Turquoise: A semi-translucent to opaque gem, turquoise typically does not exhibit the brilliance of more transparent gemstones. Its quality is assessed based on color, matrix (the remnants of the host rock), and texture. A dense, even texture results in a better polish luster, while coarser textures are less desirable. The most valuable turquoise displays a bright “robin’s egg” or “sky” blue color with even distribution and minimal undertones.
Blue Zircon: Zircon exhibits a wide range of colors, but blue zircon is the most popular. Most blue zircon is heat-treated to achieve its color, often with greenish undertones. Zircon’s color can be affected by radioactive decay over time, altering its crystalline structure and properties. “High zircon” varieties, typically blue or colorless, are preferred in jewelry due to their stability.
Tanzanite: Tanzanite is known for its strong pleochroism, meaning it displays different colors when viewed from different angles. It can exhibit shades of purple, blue, and violet. The most valuable tanzanite displays a vibrant, pure blue color, though bright purplish-blue and violet-blue are also highly sought after.
The following table summarizes key gemological properties:
| Gemstone | Chemical Composition | Color(s) | Hardness (Mohs) | Transparency |
|---|---|---|---|---|
| Turquoise | Hydrated Phosphate of Copper and Aluminum | Blue to Green | 5-6 | Opaque |
| Blue Zircon | Zirconium Silicate (ZrSiO4) | Blue (often heat-treated) | 6.5-7.5 | Transparent to Opaque |
| Tanzanite | Calcium Aluminum Silicate (Zoisite) | Blue, Violet, Purple | 6-7 | Transparent |
Symbolism and Metaphysical Beliefs
Throughout history, these gemstones have been attributed with various symbolic meanings and metaphysical properties. Turquoise has long been considered a stone of protection, believed to guarantee health and good fortune. Medieval beliefs held that it would prevent falls, particularly from horses, and even break into pieces to warn of impending disaster. Hindu mystics believed that viewing turquoise after a new moon would bring wealth.
Zircon, while not as widely associated with specific metaphysical beliefs as turquoise, has been linked to prosperity and wisdom. Different colors of zircon were believed to possess different powers.
Tanzanite, being a more recently discovered gem, has fewer established traditional beliefs. However, it is often associated with transformation, intuition, and spiritual growth.
Evaluating Quality and Care
Gemstone quality is typically assessed based on the “Four Cs”: color, cut, clarity, carat weight, and treatments. Turquoise is uniquely graded on color, matrix, and texture. For tanzanite and zircon, color is a primary factor, with vibrant, saturated hues commanding higher prices. Cut is also important, maximizing brilliance and minimizing flaws. Clarity refers to the absence of inclusions or blemishes.
Due to their varying hardness levels, these birthstones require different care. Turquoise, being relatively soft, is susceptible to scratches and should be protected from harsh impacts. Cleaning should be done gently with a soft cloth and mild soap. Zircon and tanzanite, being harder, are more durable but should still be handled with care. Avoid ultrasonic cleaners and harsh chemicals, as these can damage the stones. Regular cleaning with a soft brush and warm, soapy water is recommended.
Conclusion
December’s birthstones – Tanzanite, Turquoise, Blue Zircon, and Blue Topaz – offer a captivating array of colors, histories, and symbolic meanings. From the ancient origins of turquoise to the modern discovery of tanzanite, these gems represent a rich tapestry of geological processes and cultural traditions. Whether chosen for their beauty, their perceived metaphysical properties, or their connection to a specific month, these December birthstones continue to enchant and inspire.