December holds a unique distinction in the gemological calendar. While most months are assigned a single birthstone, December boasts four officially recognized gems: Turquoise, Blue Zircon, Tanzanite, and Blue Topaz. This abundance of choice reflects a fascinating evolution in the tradition of birthstones, blending ancient history with modern discovery. All four stones share a common thread: they possess cool, blue hues that evoke the icy skies and deep waters of the winter season. From the opaque, sky-blue Turquoise cherished by ancient civilizations to the vivid, violet-blue Tanzanite discovered only recently, these gems offer a diverse palette for collectors and jewelry enthusiasts.
The expansion of December’s birthstone list is a relatively modern phenomenon. Originally, only Turquoise and Zircon were associated with the month. However, as new gemstones were discovered and commercial interest grew, the list was updated. The National Association of Jewelers standardized the list in 1912, with updates in 1952 adding Blue Zircon, and most recently in 2002, the Jewelry Industry Council of America added Tanzanite. This article provides an in-depth exploration of these four December birthstones, examining their geological origins, gemological properties, historical lore, and symbolism, offering a guide for those born in this gem-rich month.
History and Lore
The tradition of birthstones is rooted in ancient history, with origins traced back to Mesopotamia and later adopted by the Greeks and Romans. The specific association of gems with months evolved from the twelve stones found in the Breastplate of Aaron, as described in the Book of Exodus. Over centuries, these religious and mystical connections transformed into the modern practice of wearing a specific gemstone for the month of one's birth.
Turquoise stands as the oldest and most traditional of the December birthstones. Its history spans thousands of years, with evidence of its use found across ancient cultures. It has been treasured as a stone of protection, good fortune, and friendship. Many cultures, particularly in Tibet and the Middle East, regarded Turquoise as a sacred stone, often used in spiritual rituals and as a powerful amulet. Persian turquoise, sourced from ancient mines in Iran, is historically the most prized variety, celebrated for its vivid, evenly saturated sky-blue color and minimal matrix.
Blue Zircon carries a history of confusion due to its frequent misidentification with other blue stones, such as sapphire, throughout history. Despite this, it has been valued for centuries for its brilliance and fire. In the 20th century, specifically in 1952, Blue Zircon was officially added to the list of December birthstones, solidifying its place as a traditional choice.
Blue Topaz, while having an exact historical origin that remains unknown, has been found and utilized throughout history. Its addition to the December list is a more modern development, appreciated for its durability and the availability of large, clean stones in a range of blue shades. It is notably the official state gem of Texas.
Tanzanite is the most recent addition, having been added to the birthstone list in 2002. Discovered in the 20th century in a single location in Tanzania, its rapid rise to prominence is a testament to its unique beauty and rarity. It represents the modern evolution of birthstone lists, reflecting new gemological discoveries and their commercial appeal.
Geological Formation and Sources
Each of the December birthstones forms under distinct geological conditions, contributing to their unique characteristics and rarity.
Turquoise is a phosphate mineral that forms near the surface of the earth in arid regions. It is a secondary mineral, meaning it is deposited by circulating groundwater that contains dissolved copper and aluminum. This process occurs in porous rock over long periods. Major sources for Turquoise include Iran (historically the source of the finest Persian turquoise), the United States (notably Arizona's Sleeping Beauty Mine, known for its pure, robin's-egg blue color), Tibet, and India.
Blue Zircon is a mineral belonging to the zircon family. While zircon is a common mineral found in many types of rock, the gem-quality blue variety is rarer. The blue color in gem zircon is typically the result of heat treatment of brown zircon crystals. Sources for zircon include Sri Lanka, Cambodia, and Australia, among others. The chunks provided do not specify the exact geological formation process for Blue Zircon, only that it is a gem-quality mineral.
Blue Topaz is a silicate mineral containing fluorine and aluminum. It forms in igneous rocks like granite and pegmatites, and also in metamorphic rocks. It is often found in large crystal masses. The chunks indicate that today, Blue Topaz is mined in Sri Lanka, Brazil, Mexico, Nigeria, and the U.S. The deep blue color often seen in commercial Blue Topaz is typically achieved through irradiation and heat treatment of colorless or pale topaz crystals.
Tanzanite is the trade name for the blue-violet variety of the mineral zoisite. It is an exceptionally rare gemstone because it is found in only one known location in the world: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. Its formation is linked to a specific geological event involving the heating of zoisite crystals, which occurred naturally over millions of years. This localized occurrence makes Tanzanite significantly rarer than diamond, and its value is driven by this scarcity.
Gemological Properties
Understanding the physical and chemical properties of these gems is crucial for selection, care, and appreciation. The following table summarizes key data derived from the provided sources.
| Gemstone | Mineral Group | Chemical Composition | Mohs Hardness | Typical Colors | Key Characteristics |
|---|---|---|---|---|---|
| Turquoise | Phosphate | Hydrated copper/aluminum phosphate | 5 – 6 | Sky blue, greenish-blue | Often opaque with "matrix" veining; prized for even color. |
| Blue Zircon | Zircon | Zirconium silicate (ZrSiO₄) | Not specified in sources | Bright, clear blue | Known for its high brilliance and fire. |
| Tanzanite | Zoisite | Calcium aluminum hydroxyl sorosilicate | Not specified in sources | Rich violet-blue | Exhibits trichroism (showing blue, violet, and reddish hues); most valuable of the four. |
| Blue Topaz | Topaz | Fluorine-containing aluminum silicate | 8 | Various shades of blue | Most durable December birthstone; hardest on the Mohs scale among the four. |
Turquoise is the softest of the four, with a Mohs hardness of 5 to 6. This makes it more susceptible to scratching and damage, requiring careful handling. It is typically opaque to semi-transparent. The most valued Turquoise exhibits a uniform, vibrant color, such as the pure sky-blue of Persian or Sleeping Beauty turquoise, or a strong greenish-blue. Many stones display a dark, web-like pattern known as "matrix," which is remnants of the host rock.
Blue Topaz is the most durable, with a Mohs hardness of 8. This makes it an excellent choice for everyday wear, particularly in rings and bracelets. It is a hard, vitreous mineral that can be found in large, clean crystals. The color of natural blue topaz is usually pale, but the commercially available stones are often a deep, saturated blue achieved through treatment.
Tanzanite is prized for its intense blue-violet color, which can shift depending on the light and viewing angle, a property known as trichroism. While the sources do not specify its hardness, it is generally known in the gemological community to be softer than quartz (Mohs 7) and requires protective settings for jewelry. Its rarity and unique color make it the most valuable of the December birthstones.
Blue Zircon is noted for its exceptional brilliance and fire, which can rival that of diamond. It is generally a durable stone, though specific hardness data is not provided in the sources. Its color is typically a bright, vivid blue. The sources do not detail the treatment process for blue zircon, but it is widely known in the industry that the blue color is usually the result of heating brown zircon.
Symbolism and Metaphysical Beliefs
The December birthstones are rich in symbolism and are believed to possess various metaphysical properties, offering benefits to those who wear them.
Turquoise is widely associated with protection, truth, and calmness. It is considered a steadying force, offering grounding and a sense of tranquility. Many cultures view it as a stone of good fortune and friendship, believed to ward off negative energy and bring prosperity.
Tanzanite symbolizes transformation, growth, and new beginnings. Its unique blue-violet hue is said to represent stepping into new chapters of life with clarity and curiosity. It is linked to shifts in consciousness and spiritual awakening.
Blue Zircon is known for its association with clarity, wisdom, and mental focus. It is believed to sharpen the mind, boost mental clarity, and bring a sense of balance to the wearer.
Blue Topaz, while less explicitly defined in the metaphysical beliefs provided, is generally associated with calmness, love, and good fortune. Its crisp winter blue color evokes serenity and clear communication.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones, with their differing hardness levels dictating specific handling instructions.
Turquoise, with its low hardness of 5-6, is the most delicate. It is susceptible to scratching from harder materials and can be damaged by chemicals, perfumes, and cosmetics. Cleaning should be done gently with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaning.
Blue Zircon and Tanzanite are also softer than many other gemstones and should be handled with care to prevent chipping or scratching. While specific cleaning instructions are not provided in the sources, standard practice for these stones involves using warm, soapy water and a soft brush. It is advisable to store them separately from other jewelry to avoid contact with harder gems.
Blue Topaz, being the hardest at 8, is more resilient and suitable for daily wear. It can be cleaned with warm, soapy water and a soft brush. However, like all colored gemstones, it should be protected from sudden temperature changes and harsh chemicals. Its durability makes it a practical choice for a birthstone that will be worn frequently.
Conclusion
The four birthstones of December—Turquoise, Blue Zircon, Tanzanite, and Blue Topaz—offer a remarkable range of choices for those born in the final month of the year. Each gem possesses a distinct identity, from the ancient, protective Turquoise to the rare and transformative Tanzanite. Their shared blue color palette connects them to the winter season, while their diverse origins, properties, and histories provide a rich field for exploration. Whether one is drawn to the durability of Blue Topaz, the brilliant fire of Blue Zircon, or the unique rarity of Tanzanite, there is a December gemstone to suit every preference and style. This variety is a testament to the dynamic nature of birthstone tradition, a practice that continues to evolve while honoring the timeless allure of the earth's treasures.