December is unique among the calendar months, boasting not one, but four recognized birthstones: blue topaz, turquoise, zircon, and tanzanite. These gemstones, each with its own distinct history, properties, and appeal, offer a wide range of choices for those born in the final month of the year. All four stones share a common thread – a connection to shades of blue, perfectly mirroring the cool tones of the winter season.
History and Lore
The history of December’s birthstones is varied, spanning millennia and encompassing diverse cultures. Turquoise holds the longest documented history, having been prized for thousands of years. Ancient Egyptians, including pharaohs, adorned themselves with turquoise, and Chinese artisans were carving the stone more than 3,000 years ago. Throughout history, turquoise was believed to possess protective powers, safeguarding wearers from harm, even preventing falls from horses. Hindu traditions associated the stone with wealth and good fortune when viewed after a new moon.
Zircon, while also ancient in origin, has a more complex history tied to its varied colors. The name “jargon” was historically used for lighter yellow zircons, while “hyacinth” or “jacinth” referred to the reddish-brown varieties.
Tanzanite, in contrast, is a relatively recent discovery. Found in the foothills of Mount Kilimanjaro, its introduction to the gem market is a 20th-century phenomenon. Blue topaz, while topaz itself has been known for centuries, the popularity of blue topaz as a birthstone is a more modern development, often achieved through heat treatment.
Geological Formation and Sources
The origins of these gemstones are as diverse as their histories. Turquoise is a secondary mineral, forming from hydrated copper aluminum phosphate, typically in arid regions. Its characteristic matrix – the remnants of the host rock – often contributes to its unique appearance.
Zircon forms in igneous rocks and metamorphic rocks, and can be found in a wide range of geological settings. Its formation involves complex processes related to magma crystallization and metamorphic transformations. The varying colors of zircon are linked to trace elements and radioactive decay within its crystal structure.
Tanzanite is found in a very limited geographical area: the Merelani Hills of northern Tanzania. It forms within metamorphic rocks and is known for its strong trichroism, displaying different colors depending on the viewing angle.
Blue topaz is typically created through the irradiation and heat treatment of colorless or pale topaz. Natural blue topaz is rare. Topaz itself forms in igneous rocks, particularly granites and rhyolites, and is often found in pegmatites.
Gemological Properties
Each of December’s birthstones possesses unique gemological properties. Turquoise is a semi-translucent to opaque gem, ranging in color from blue to green. Its value is often determined by the intensity of its blue hue, the evenness of its color distribution, and the quality of its matrix.
Zircon exhibits a wide range of colors, but blue zircon is the most popular for December birthstones. It is often heat-treated to achieve this color. Zircon’s refractive index and dispersion contribute to its brilliance. However, it’s important to note that some zircons undergo metamictization over time due to radioactive decay, potentially affecting their clarity and color. “High zircon” varieties are generally preferred for jewelry due to their greater stability.
Tanzanite is known for its vibrant purple to blue hues. The most valuable colors are strong, pure blue and violet-blue. Tanzanite also exhibits strong pleochroism, meaning it displays different colors when viewed from different angles. Its tone, ideally between 75 and 85 percent, significantly impacts its value.
Blue topaz, often created through treatment, displays varying shades of blue, sometimes with greenish undertones. The intensity and purity of the blue color are key factors in determining its quality.
The following table summarizes key properties:
| Gemstone | Color(s) | Transparency | Hardness (Mohs) | Chemical Composition |
|---|---|---|---|---|
| Turquoise | Blue to Green | Opaque | 5-6 | Hydrated Copper Aluminum Phosphate |
| Zircon | Blue, Green, Yellow, Red | Transparent | 6.5-7.5 | Zirconium Silicate (ZrSiO₄) |
| Tanzanite | Purple to Blue | Transparent | 6-7 | Calcium Aluminum Silicate |
| Blue Topaz | Blue | Transparent | 8 | Aluminum Silicate Fluoride |
Symbolism and Metaphysical Beliefs
Throughout history, these gemstones have been imbued with symbolic meaning. Turquoise has long been associated with protection, good fortune, and health. Ancient cultures believed it could ward off evil and prevent accidents.
Zircon, depending on its color, has been linked to various properties. Blue zircon is often associated with wisdom and prosperity.
Tanzanite is considered a stone of transformation, believed to facilitate spiritual growth and enhance intuition.
Blue topaz is often associated with communication, loyalty, and emotional balance. It is thought to promote clarity of thought and inspire creativity.
Care and Cleaning
The care required for each of these gemstones varies based on their hardness and other properties. Turquoise, being relatively soft, is susceptible to scratches and damage from harsh chemicals. It should be cleaned with a soft cloth and mild soap and water. Avoid ultrasonic cleaners and harsh cleaning agents.
Zircon, with its good hardness, is more durable but can still be chipped or scratched. It can be cleaned with warm, soapy water and a soft brush.
Tanzanite is also relatively durable but can be damaged by sudden temperature changes. It should be cleaned with warm, soapy water and a soft brush. Avoid ultrasonic cleaners.
Blue topaz, being a hard and durable stone, can be cleaned with warm, soapy water and a soft brush. Ultrasonic cleaners can be used with caution.
December Birthstone by Day
Interestingly, a more granular assignment of birthstones exists for each day of December. According to one source, the birthstone assignment varies throughout the month: Blue Topaz and Tanzanite are assigned to multiple days, as is Turquoise and Blue Zircon.
| Date | Birthstone |
|---|---|
| Dec 4 | Blue Topaz |
| Dec 5 | Tanzanite |
| Dec 6 | Turquoise |
| Dec 7 | Blue Zircon |
| Dec 8 | Blue Topaz |
| Dec 9 | Tanzanite |
| Dec 10 | Turquoise |
| Dec 11 | Blue Zircon |
| Dec 12 | Blue Topaz |
| Dec 13 | Tanzanite |
| Dec 14 | Turquoise |
| Dec 15 | Blue Zircon |
| Dec 16 | Blue Topaz |
| Dec 17 | Tanzanite |
| Dec 18 | Turquoise |
| Dec 19 | Blue Zircon |
| Dec 20 | Blue Topaz |
| Dec 21 | Tanzanite |
| Dec 22 | Turquoise |
| Dec 23 | Blue Zircon |
| Dec 24 | Blue Topaz |
| Dec 25 | Tanzanite |
| Dec 26 | Turquoise |
| Dec 27 | Blue Zircon |
| Dec 28 | Blue Topaz |
| Dec 29 | Tanzanite |
| Dec 30 | Turquoise |
| Dec 31 | Blue Zircon |
Conclusion
December’s birthstones – turquoise, tanzanite, zircon, and blue topaz – represent a captivating array of colors, histories, and symbolic meanings. From the ancient protective powers of turquoise to the modern allure of tanzanite, these gemstones offer a unique connection to the winter season and a wealth of choices for those seeking a meaningful and beautiful adornment. Their versatility allows them to be incorporated into a wide range of jewelry styles, making them timeless treasures for generations to come.