December is uniquely represented by three birthstones: Turquoise, Zircon, and Tanzanite. Among these, Tanzanite stands out as a gemstone of extraordinary rarity and modern allure. Discovered only in the 20th century, this blue-to-violet variety of zoisite has rapidly ascended the ranks of the gemological world, captivating collectors and jewelry enthusiasts with its singular beauty and compelling origin story. This article delves into the science, history, and symbolism of Tanzanite, providing a detailed exploration of this remarkable December birthstone.
History and Lore
Tanzanite’s history is remarkably brief, a stark contrast to gemstones that have been revered for millennia. Its story begins in 1967, not in an ancient mine, but in the foothills of Mount Kilimanjaro. A Maasai herder named Ali Juuyawatu Saitote discovered a cluster of brilliant blue crystals in the Merelani Hills of northern Tanzania. Initially, these stones were mistaken for sapphires, but their distinct properties soon revealed a new gem to the world.
The discovery was formally documented by a local tailor, Manuel de Souza, who brought the stones to the attention of gemologists. Geologist John Saul, who was surveying the area at the time, recognized the potential of the find and conducted further exploration, leading to the identification of a commercial deposit. The gem was named “tanzanite” in honor of its country of origin by Tiffany & Co., which introduced the stone to the global market in 1968. The company’s marketing campaign, highlighting the stone’s rarity and unique color, was instrumental in its rapid popularity.
Despite its recent introduction, Tanzanite has already accumulated its own lore. It is often associated with transformation and new beginnings, a fitting metaphor for its sudden appearance on the gemological scene. Some modern spiritual circles attribute calming and meditative properties to the stone, though these beliefs are not rooted in historical tradition. Its designation as a December birthstone is a modern convention, solidified by the American Gem Trade Association (AGTA) and the Jewelers of America (JA) to provide a contemporary option for those born in the final month of the year.
Geological Formation and Sources
Tanzanite’s geological formation is as unique as its discovery. It is a variety of the mineral zoisite, specifically the blue to violet-blue form caused by the presence of vanadium within its crystal structure. The conditions required for its formation are exceptionally rare, which directly explains why Tanzanite is found in only one location on Earth.
The primary and currently the only commercial source of Tanzanite is a small, four-square-kilometer mining area in the Merelani Hills of the Manyara Region in northern Tanzania. This area is situated at the base of Mount Kilimanjaro, the highest peak in Africa. The gem forms in a specific geological environment: a hydrothermal alteration of the host rock, which is a type of metamorphic rock. The process involves the interaction of hot, mineral-rich fluids with the surrounding rock, leading to the crystallization of zoisite. The presence of vanadium is the key factor that imparts the coveted blue color.
Mining operations in the Merelani Hills vary in scale, from large-scale commercial ventures to smaller, artisanal operations. The mining process is challenging due to the hard nature of the host rock and the often complex and fragmented vein structures of the gem crystals. This contributes to the stone’s rarity and value. There are no known commercial deposits of natural Tanzanite outside of this specific region in Tanzania, a fact that underscores its status as a “one-generation” gemstone, as some geologists have noted, given that the deposit may be exhausted within a few decades.
Gemological Properties
Tanzanite possesses a distinct set of physical and optical characteristics that define its identity and value in the gem market. Understanding these properties is crucial for identification, appraisal, and care.
Chemical Composition and Crystal Structure: Tanzanite is a member of the epidote mineral group, with the chemical formula Ca₂Al₃(SiO₄)₃(OH). Its crystal system is orthorhombic. The distinctive blue to violet color is not inherent to the mineral zoisite but is the result of trace amounts of vanadium substituting for aluminum in the crystal lattice. In its natural state, Tanzanite often appears brownish or greenish; the desirable blue hue is typically achieved through a controlled heat treatment process, which is considered a standard and permanent enhancement.
Color: The color range of Tanzanite is one of its most celebrated features. It can exhibit a pure blue, a vivid violet, or a blend of both, often with pleochroism—displaying different colors when viewed from different angles. Under incandescent light, the violet tones are often more pronounced, while in daylight or fluorescent light, the blue component dominates. The most valuable Tanzanite stones display a rich, saturated violet-blue hue, free of muddy or overly dark undertones.
Hardness and Durability: On the Mohs scale of mineral hardness, Tanzanite has a rating of 6.5 to 7. This places it in the category of moderately hard gemstones. While it is suitable for most types of jewelry, it is not as hard as corundum (sapphire and ruby, Mohs 9) or topaz (Mohs 8). This means Tanzanite can be scratched by harder materials and should be handled with care. It also possesses perfect cleavage in one direction, making it susceptible to chipping or breaking if struck with force, especially along certain planes. This property necessitates protective settings, such as bezels or halo settings, for rings and bracelets that may be exposed to impact.
Clarity and Inclusions: Tanzanite is typically found with good to excellent clarity. It is an "eye-clean" stone, meaning inclusions are not visible to the naked eye. However, like many natural gemstones, it can contain inclusions such as minute mineral crystals, fingerprints, or veils. The presence of visible inclusions can affect transparency and value, but well-cut Tanzanite often appears remarkably clear and luminous.
Refractive Index and Specific Gravity: Tanzanite has a refractive index ranging from 1.691 to 1.700, which contributes to its brilliance when properly cut. Its specific gravity is approximately 3.35, a measure of its density. These optical properties are key identifiers for gemologists distinguishing Tanzanite from visually similar stones like sapphire or amethyst.
Cut and Carat Weight: Tanzanite is cut into a variety of shapes to maximize its color and brilliance. Common cuts include oval, pear, cushion, and emerald cuts, which can enhance the depth of its blue-violet hue. Larger faceted Tanzanite stones are relatively rare and command a significant premium per carat. While stones of over 10 carats have been found, they are exceptional and primarily reside in museum collections or the hands of serious collectors.
The following table summarizes the key gemological properties of Tanzanite:
| Property | Specification |
|---|---|
| Mineral Species | Zoisite |
| Chemical Formula | Ca₂Al₃(SiO₄)₃(OH) |
| Crystal System | Orthorhombic |
| Mohs Hardness | 6.5 - 7 |
| Cleavage | Perfect in one direction |
| Refractive Index | 1.691 - 1.700 |
| Specific Gravity | 3.35 |
| Typical Treatments | Heat (to enhance color) |
| Primary Source | Merelani Hills, Tanzania |
Symbolism and Metaphysical Beliefs
While Tanzanite lacks the ancient historical lore of stones like emerald or ruby, it has quickly accrued a rich tapestry of modern symbolism and metaphysical associations. Its rapid rise to prominence has allowed it to be woven into contemporary spiritual and healing practices.
In the realm of modern crystal healing, Tanzanite is often referred to as a stone of transformation. It is believed to facilitate spiritual awakening and higher consciousness, helping the wearer to connect with their higher self and perceive life with a new perspective. Its striking color, which shifts between blue and violet, is seen as a metaphor for bridging the gap between the physical and spiritual realms. Some practitioners associate Tanzanite with the throat and third eye chakras, promoting clear communication, intuition, and psychic abilities.
As a December birthstone, Tanzanite carries specific meanings for those born in that month. It is said to represent wisdom, clarity, and truth. Gifting a Tanzanite is often seen as a gesture of good fortune and a wish for the recipient’s journey to be filled with profound insight and positive change. Its rarity and unique origin story also lend it an aura of exclusivity and preciousness, making it a meaningful symbol for personal milestones and achievements.
It is important to note that these metaphysical beliefs are part of modern alternative practices and are not supported by scientific evidence. However, for many, the symbolic value of Tanzanite enhances its personal significance and emotional resonance.
Care and Cleaning
Given its specific physical properties, Tanzanite requires attentive care to maintain its beauty and integrity over time. The gemstone’s moderate hardness and perfect cleavage mean it is more vulnerable to damage than some of its more durable counterparts.
Daily Wear Considerations: Tanzanite is best suited for jewelry that is less likely to encounter impact, such as pendants, earrings, and brooches. When worn in rings, it should be set in a protective setting, like a bezel or a halo, to shield the stone’s edges from knocks. It is advisable to remove Tanzanite jewelry before engaging in physical activities, gardening, or household chores where it could be struck or exposed to abrasive materials.
Cleaning Methods: To clean Tanzanite, use warm water, a mild dish soap, and a soft brush (such as a baby’s toothbrush). Gently scrub the stone and its setting, then rinse thoroughly to remove any soap residue. Avoid using ultrasonic cleaners, as the vibrations can potentially cause the stone to fracture along its cleavage planes. Steam cleaning is also not recommended, as sudden temperature changes can stress the stone. After cleaning, dry the jewelry with a soft, lint-free cloth.
Storage: When not being worn, store Tanzanite jewelry separately from other jewelry pieces to prevent scratches. A soft pouch or a lined compartment in a jewelry box is ideal. Keep it away from direct sunlight and extreme heat for prolonged periods, as this can potentially affect the color of some treated stones, although the heat treatment of Tanzanite is generally stable under normal conditions.
Conclusion
Tanzanite is a gemstone that encapsulates the wonder of modern discovery. From its serendipitous finding in the foothills of Mount Kilimanjaro to its status as a celebrated December birthstone, it represents a unique chapter in gemological history. Its captivating blue-to-violet hues, a product of a singular geological formation, are matched by its scientific intrigue and symbolic depth.
While its journey in the market has been brief, its impact is undeniable. Tanzanite offers a compelling narrative of rarity, transformation, and beauty, making it a cherished choice for collectors, jewelry enthusiasts, and anyone born in December. As a stone that is mined in only one location on Earth, it serves as a poignant reminder of the Earth’s precious and finite treasures. With proper care and appreciation for its unique properties, a piece of Tanzanite can be a lifelong companion, a symbol of insight and elegance for generations to come.