Tanzanite, a gemstone of extraordinary rarity and captivating color, has swiftly ascended to prominence in the world of fine jewelry and gemology. Designated as a modern birthstone for the month of December, this variety of the mineral zoisite is celebrated for its unique trichroic properties and profound symbolic meanings. Its discovery in the mid-20th century introduced a new chapter in gemstone history, offering a vibrant, blue-violet alternative to traditional December stones. This article provides a comprehensive exploration of tanzanite, detailing its geological origins, historical journey to becoming a birthstone, distinctive gemological characteristics, and the cultural significance it holds for those born in December. Drawing from authoritative sources, we will examine the science, lore, and care of this remarkable gemstone, which continues to enchant gem enthusiasts and jewelry buyers worldwide.
History and Lore
Tanzanite is a relatively recent addition to the gemological world, with a history that spans only a few decades. Unlike ancient gemstones with millennia of lore, tanzanite’s story begins in the 1960s. It was first discovered in 1967 in the Merelani Hills of Northern Tanzania, a region near the majestic Mount Kilimanjaro. The gemstone’s discovery is attributed to a local Maasai herder who noticed blue crystals in the area, which were subsequently brought to the attention of geologists. This event marked the beginning of a journey that would see the stone become a global sensation.
The mineral zoisite, to which tanzanite belongs, was first identified in the 19th century. However, the blue variety that constitutes tanzanite was unknown until its discovery in Tanzania. The gemstone’s international fame was largely propelled by the jewelry company Tiffany & Co., which recognized its potential and introduced it to the global market. Tiffany & Co. named the gemstone "tanzanite" in honor of its country of origin, and its marketing efforts were instrumental in establishing the stone as a desirable and luxurious gem. The company’s promotion highlighted the stone’s deep, captivating colors and its extreme rarity, noting that it is found in only one small geographic location on Earth.
The journey of tanzanite to becoming an official birthstone for December is a modern tale. For centuries, birthstone traditions have evolved, with different cultures and regions assigning specific stones to each month. The modern list of birthstones, often referenced in the United States, is largely based on a standardized list established in 1912 by the National Association of Jewelers. This list has been updated over time to include new and popular gemstones. Tanzanite was officially added to the list of birthstones for December in 2002. This designation joined traditional December stones, such as turquoise and blue zircon, providing a contemporary and vibrant option for those born in the last month of the year. Its addition reflects the gemstone’s growing popularity and its visual alignment with the wintry and festive ambiance of December.
While tanzanite lacks the ancient legends of stones like emerald or ruby, it has quickly accumulated its own symbolism. In the short time since its discovery, it has come to represent transformation, creativity, and emotional balance. This modern lore is often tied to its unique geological origin and its striking color transformation, which will be discussed in detail in subsequent sections.
Geological Formation and Sources
The geological genesis of tanzanite is as unique as the gemstone itself. It is a variety of the mineral zoisite, specifically the blue to violet-blue form. Tanzanite is not formed in the typical gemstone environments of igneous or metamorphic processes but rather through a rare and complex geological event. The stones found in the Merelani Hills are the result of a natural metamorphic process that occurred approximately 585 million years ago. During this time, intense heat and pressure from tectonic plate movements transformed limestone into the mineral zoisite, introducing trace elements like vanadium, chromium, and titanium that are responsible for its captivating colors.
What makes the formation of tanzanite particularly extraordinary is the role of a subsequent geological event. The original zoisite crystals were likely colorless or brownish. It is believed that a massive forest fire, occurring around 25 million years ago, heated the zoisite crystals to a temperature of about 600 degrees Celsius. This heat, combined with the slow cooling process, allowed the trace elements to arrange themselves within the crystal lattice, resulting in the vibrant blue and violet hues for which tanzanite is famous. This dual-stage formation process—initial metamorphism followed by a thermal event—is exceptionally rare and is a key factor in the gemstone’s scarcity.
The geographic source of tanzanite is one of its most defining characteristics. All known commercial deposits of gem-quality tanzanite are found in a small, limited area of the Merelani Hills in Northern Tanzania, near the base of Mount Kilimanjaro. This specific region, often described as being only a few square kilometers in size, is the exclusive source of this gemstone. The mining operations in this area are complex, involving both large-scale industrial efforts and small-scale artisanal mining. The concentration of tanzanite in this single location on the planet contributes significantly to its rarity. In fact, some sources note that tanzanite is considered rarer than diamonds due to its extremely limited geographic occurrence. This singular source location not only adds to the gemstone’s mystique but also presents challenges for sustainable mining and future availability.
Gemological Properties
Tanzanite possesses a set of gemological properties that make it both unique and desirable, though it also requires specific care due to its physical characteristics.
Color and Optical Phenomena: The most celebrated feature of tanzanite is its mesmerizing color. It exhibits a range from deep, royal blue to rich violet and purplish-blue. This color variation is not merely a difference in hue but is a direct result of its most famous optical property: trichroism. Trichroism is the ability of a crystal to display three distinct colors when viewed from three different crystallographic directions. In the case of tanzanite, these colors are typically blue, violet, and burgundy or reddish-brown. The specific color observed depends on the orientation of the crystal and the angle of light. Most tanzanite on the market is heat-treated to enhance its blue and violet colors, removing the brownish overtones that are naturally present. This treatment is permanent and is widely accepted in the gem trade.
Hardness and Durability: On the Mohs scale of mineral hardness, tanzanite rates between 6 and 7. This places it in the moderately durable category, making it suitable for jewelry that is worn with care, such as earrings, pendants, and occasional-wear rings. However, its hardness is lower than that of many popular gemstones like sapphire (Mohs 9) or diamond (Mohs 10). Furthermore, tanzanite has poor toughness due to its perfect cleavage in one direction. Cleavage is the tendency of a mineral to break along flat planes of weakness within its crystal structure. This means that tanzanite can be susceptible to chipping or cracking if subjected to a hard knock or impact. As a result, it is generally not recommended for rings worn daily, such as engagement rings or wedding bands, unless set in a protective mounting that minimizes the risk of impact.
Chemical and Physical Characteristics: Chemically, tanzanite is a calcium aluminum silicate, with the formula Ca₂Al₃(SiO₄)₃(OH). Its blue-violet color is primarily attributed to the presence of vanadium ions within its crystal structure. Other trace elements, such as chromium and iron, can also influence its coloration. Tanzanite has a refractive index ranging from approximately 1.69 to 1.70, which is a measure of how much light bends when entering the stone, contributing to its brilliance. It has a specific gravity of about 3.35, which is a measure of its density compared to water. These properties, combined with its trichroism, make tanzanite a gemologist's interesting subject and a jeweler's captivating centerpiece.
Cut and Clarity: Due to its strong trichroism, cutting tanzanite requires skill and precision. Cutters must orient the crystal to showcase the most desirable color—typically the rich blue or violet—and to minimize the visibility of the burgundy component. Common cuts for tanzanite include oval, cushion, pear, and emerald cuts, which help to display its color and clarity effectively. Tanzanite is often found with good clarity, though inclusions are not uncommon. As with many colored gemstones, the value of tanzanite is primarily driven by the intensity and uniformity of its color, followed by clarity, cut, and carat weight.
Summary of Key Gemological Properties
| Property | Description |
|---|---|
| Mineral Species | Zoisite |
| Chemical Formula | Ca₂Al₃(SiO₄)₃(OH) |
| Hardness (Mohs Scale) | 6 - 7 |
| Crystal System | Orthorhombic |
| Refractive Index | 1.69 - 1.70 |
| Specific Gravity | ~3.35 |
| Primary Color Range | Blue, Violet, Purplish-Blue |
| Optical Phenomenon | Strong Trichroism (Blue, Violet, Burgundy) |
| Cleavage | Perfect in one direction |
| Sources | Exclusively Merelani Hills, Tanzania |
Symbolism and Metaphysical Beliefs
While tanzanite’s history is short, its symbolism has developed rapidly and is often rooted in its unique properties and discovery story. As a modern birthstone for December, it carries meanings that resonate with the themes of the holiday season and the transition into a new year.
Transformation and New Beginnings: The most prevalent symbolic meaning associated with tanzanite is transformation. This symbolism is directly linked to its geological formation. The gemstone’s journey from a colorless or brownish zoisite to a brilliant blue-violet stone through the transformative power of heat mirrors personal growth, change, and the emergence of new perspectives. For those born in December, a month that marks the end of one year and the beginning of another, tanzanite serves as a powerful emblem of transition, encouraging the wearer to embrace change and seek new opportunities.
Emotional Balance and Creativity: Tanzanite is also believed to promote emotional balance and clarity. Its captivating colors are thought to help soothe the mind and enhance self-awareness. Many in the metaphysical community suggest that tanzanite stimulates the throat and third-eye chakras, facilitating clear communication, intuition, and creative expression. This makes it a popular stone for artists, writers, and anyone seeking to unlock their creative potential. For December babies, it is said to bring joy, inspiration, and a heightened sense of creativity to their lives.
A Stone of Modern Spirituality: Unlike traditional birthstones with centuries of accumulated lore, tanzanite’s metaphysical beliefs are part of a contemporary spiritual landscape. It is often associated with the "New Age" movement and is valued for its perceived ability to connect the physical and spiritual realms. Some believe that wearing tanzanite can facilitate a deeper connection to one's higher self and promote spiritual growth. While these beliefs are not scientifically proven, they contribute to the stone’s allure and its significance for individuals who ascribe to its symbolic meanings.
Care and Cleaning
Given its moderate hardness and perfect cleavage, tanzanite requires careful handling and specific cleaning methods to maintain its beauty and integrity. Proper care is essential to ensure the longevity of tanzanite jewelry.
Cleaning Methods: The safest way to clean tanzanite is with warm, soapy water and a soft brush. Use a mild dish soap and a soft-bristled toothbrush to gently remove any dirt or oils from the surface and settings. Rinse thoroughly with clean, lukewarm water to ensure no soap residue remains. Avoid using ultrasonic cleaners and steam cleaners, as the vibrations and high heat can potentially cause fractures or exacerbate existing inclusions, especially in stones that have been treated or have internal stress. Chemical cleaners, including ammonia or bleach-based solutions, should also be avoided as they can damage the stone or its setting.
Handling and Storage: Due to its perfect cleavage, tanzanite should be protected from hard knocks and impacts. It is advisable to remove tanzanite jewelry before engaging in physical activities, household chores, or sports. When not in use, store tanzanite pieces separately in a soft cloth-lined jewelry box or pouch to prevent them from scratching softer gems or being scratched by harder stones like diamonds or sapphires. Avoid exposing tanzanite to extreme temperature changes, which can cause thermal shock and potentially damage the stone.
Professional Maintenance: Regular inspections by a professional jeweler are recommended for all tanzanite jewelry. A jeweler can check the security of the setting, look for any signs of damage, and perform a professional cleaning. If any damage, such as a chip or crack, is noticed, it should be addressed promptly by a professional to prevent further issues. For rings intended for daily wear, a protective setting, such as a bezel or a halo with smaller stones, can help shield the tanzanite from impacts.
Conclusion
Tanzanite stands as a testament to the dynamic and ever-evolving world of gemstones. From its exclusive geological cradle in the Merelani Hills of Tanzania to its official status as a December birthstone, this zoisite variety has carved a unique niche in gemological history. Its discovery in the 1960s introduced a gemstone of unparalleled rarity, defined by its striking trichroic display of blue, violet, and burgundy. While its hardness and cleavage necessitate mindful care, its captivating beauty and rich color make it a prized possession for jewelry enthusiasts.
The symbolic meanings of transformation, emotional balance, and creativity that have been woven around tanzanite in its short history resonate deeply with the themes of its birth month. For those born in December, it offers a connection to a modern yet profound tradition, blending aesthetic splendor with personal significance. As a gemstone that is geologically finite and visually enchanting, tanzanite continues to captivate the hearts of gemologists, jewelers, and wearers alike, securing its place as a cherished and meaningful gemstone in the contemporary landscape.