Tanzanite, the newest addition to the December birthstone family, is a captivating gemstone renowned for its mesmerizing violet-blue hues and pleochroic nature. First discovered in the 20th century, it has rapidly ascended to become one of the most sought-after colored stones in the modern jewelry market. As a December birthstone, it stands alongside the ancient turquoise and the fiery zircon, offering a contemporary choice for those born in the final month of the year. Its unique color, which shifts dramatically depending on the viewing angle, and its limited geographic origin contribute to its allure and value. This article explores the geological formation, gemological properties, historical journey, symbolism, and care of tanzanite, drawing exclusively from authoritative sources to provide a comprehensive guide for gemstone enthusiasts and collectors.
History and Lore
Unlike many gemstones with millennia of human history, tanzanite’s story is remarkably recent. It entered the gemological world in the late 1960s, making it a distinctly modern birthstone. Its discovery is attributed to a Maasai herdsman who, in 1967, found blue crystals near Mount Kilimanjaro in Tanzania. These crystals were later identified as a new variety of the mineral zoisite. The gemstone’s rapid rise to fame was orchestrated by the jewelry giant Tiffany & Co., which recognized its potential and launched a major marketing campaign in 1968, branding it "tanzanite" after its country of origin.
Tanzanite’s status as a birthstone is also a product of modern curation. It was formally added to the official list of birthstones for December in 2002. Prior to this, the primary December birthstones were turquoise and zircon. The inclusion of tanzanite reflected its growing popularity and the desire to offer a wider range of choices to consumers. This evolution demonstrates how birthstone lists are not static but can be updated to include newly discovered and culturally significant gemstones. The addition of tanzanite provided a vibrant, blue alternative to the traditional options, appealing to contemporary tastes while maintaining the month’s thematic connection to the color blue.
The lore surrounding tanzanite is primarily modern and often tied to its metaphysical attributes rather than ancient legends. As a new stone, it lacks the extensive historical narratives of gems like turquoise or zircon. However, its unique color-changing property has inspired its own set of beliefs. Some modern sources attribute it with the ability to foster a higher consciousness and facilitate a connection between the physical and spiritual worlds. Its striking violet-blue color is often associated with calmness and clarity, making it a popular choice for those seeking a gemstone with both visual and perceived spiritual appeal.
Geological Formation and Sources
Tanzanite’s geological story is as unique as its color. It is found in only one location on Earth: the Merelani Hills of northern Tanzania, near the foothills of Mount Kilimanjaro. This extremely limited geographic source makes it one of the rarest gemstones in the world, with some geologists estimating that the current deposits could be depleted within a few decades. The formation of tanzanite is linked to a specific geological event: the intense heat and pressure that transformed zoisite into tanzanite during a metamorphic process. This event was localized, which explains why the gemstone is not found elsewhere.
The primary mining area is the Merelani block, which is divided into four sections. While small-scale mining occurs, the most significant commercial production comes from larger mining operations. The rough tanzanite crystals are often found in a brownish-orange color, which is actually the original form of the mineral before it is heat-treated. This treatment is a crucial step in bringing out the gemstone’s signature blue-to-violet colors.
The sourcing of tanzanite is a critical factor in its market value and ethical considerations. Because it comes from a single, small geographic area, the supply chain can be complex. Responsible sourcing is a growing concern in the gem trade, and many reputable dealers now emphasize traceable and ethically sourced tanzanite. The limited origin also contributes to its rarity and, consequently, its price, especially for larger, high-quality stones. As with many colored gemstones, the value is influenced not only by the four Cs (color, clarity, cut, and carat) but also by the provenance and ethical standards of its extraction.
Gemological Properties
Tanzanite is a variety of the mineral zoisite, specifically the blue to violet-blue variety. Its chemical formula is Ca₂Al₃(SiO₄)₃(OH), and it belongs to the sorosilicate family. Understanding its gemological properties is essential for identifying, valuing, and caring for this unique birthstone.
One of tanzanite’s most defining characteristics is its pleochroism. This is the property of a gemstone to show different colors when viewed from different crystal directions. In the case of tanzanite, it typically displays three distinct colors: blue, violet, and red-violet. The primary color observed depends on the orientation of the crystal during cutting. Most tanzanite sold in jewelry is cut to show the desirable blue-to-violet hue from the top, while the red-violet flashes may be visible from other angles. This dynamic color play is a major part of its appeal and is often highlighted in jewelry design.
Color is the most critical factor in determining tanzanite’s value. The most prized colors are a rich, saturated violet-blue or a deep royal blue. Lighter shades, which may appear more lavender or gray, are generally less valuable. The intense blue color is almost always the result of heat treatment. Natural, unheated tanzanite is extremely rare and typically exhibits a brownish-orange hue. The heat treatment process is stable and permanent, and it is an accepted industry practice that enhances the gemstone’s color to meet market expectations.
Clarity is another important consideration. High-quality tanzanite is typically very clean, with few inclusions visible to the naked eye. However, like many colored stones, it can have natural inclusions such as fingerprints, needles, or minute mineral crystals. These inclusions do not necessarily detract from the stone’s beauty if they do not affect its transparency or durability. Eye-clean stones are the standard for fine tanzanite jewelry.
Cut is crucial for maximizing tanzanite’s color and minimizing its inherent weaknesses. Because tanzanite has perfect cleavage in one direction, it requires a skilled cutter to avoid creating facets that could lead to chipping. Common cuts include oval, round, pear, and emerald cuts. The cut must be precise to ensure the stone displays the best possible color from the table (top) of the gem.
Hardness and Durability: On the Mohs scale of hardness, tanzanite measures 6.5 to 7. This places it in the moderately durable category, meaning it is suitable for jewelry but requires careful handling. It is softer than quartz (7) and significantly softer than sapphire or diamond (9-10). Its perfect cleavage makes it susceptible to chipping or cracking if struck with force. Therefore, tanzanite is not recommended for rings that will endure daily wear and tear, such as engagement rings. It is better suited for earrings, pendants, and occasional-wear rings where the risk of impact is lower.
Refractive Index and Specific Gravity: While not typically a focus for casual buyers, these properties help gemologists identify tanzanite. Its refractive index ranges from 1.691 to 1.700, and its specific gravity is between 3.35 and 3.38. These figures distinguish it from other blue gemstones like sapphire or topaz.
The following table summarizes key gemological properties of tanzanite based on the provided sources:
| Property | Description |
|---|---|
| Mineral Species | Zoisite |
| Chemical Formula | Ca₂Al₃(SiO₄)₃(OH) |
| Color | Blue to bluish purple to bluish violet; often pleochroic (blue, violet, red-violet) |
| Hardness (Mohs) | 6.5 - 7 |
| Cleavage | Perfect in one direction |
| Luster | Vitreous (glass-like) |
| Transparency | Transparent to translucent |
| Primary Source | Merelani Hills, Tanzania (only known source) |
| Common Treatments | Heat treatment (to enhance blue/violet color) |
Symbolism and Metaphysical Beliefs
As a modern gemstone, tanzanite’s symbolism is largely derived from its color, rarity, and the beliefs assigned to it by contemporary crystal healers and jewelers. Its deep blue-violet hue is often linked to spiritual awareness and transformation. Some metaphysical beliefs suggest that tanzanite can facilitate a connection between the physical and spiritual realms, promoting higher consciousness and intuition. It is sometimes referred to as a "stone of magic" due to its striking color and alleged ability to enhance psychic abilities.
The gemstone’s association with December and its birthstone status adds another layer of meaning. December is often seen as a month of reflection, closure, and anticipation for the new year. The calming, serene colors of tanzanite are thought to complement this introspective period, encouraging peace and clarity. For those born in December, wearing tanzanite is believed to bring good fortune, protection, and a sense of balance.
It is important to note that these metaphysical interpretations are not supported by scientific evidence and are considered beliefs within certain cultural or spiritual practices. The gemological community values tanzanite primarily for its physical beauty and geological rarity. However, the symbolic meanings add a personal dimension for many owners, enhancing the emotional connection to the stone.
Care and Cleaning
Given its moderate hardness and perfect cleavage, tanzanite requires specific care to maintain its beauty and integrity. Proper maintenance is essential to prevent scratches, chips, and damage to its surface.
Cleaning: The safest method for cleaning tanzanite is using warm, soapy water and a soft brush. Avoid harsh chemicals, ultrasonic cleaners, and steam cleaners, as these can damage the stone or its settings. Sudden temperature changes can also be harmful. After cleaning, rinse thoroughly with clean water and dry with a soft, lint-free cloth. For regular maintenance, a gentle wipe with a microfiber cloth can help remove fingerprints and oils.
Storage: When not in use, store tanzanite jewelry separately from other pieces to prevent scratches. Soft pouches or lined jewelry boxes are ideal. Avoid storing it in direct sunlight for prolonged periods, as intense light and heat could potentially affect some treated stones, although tanzanite is generally stable.
Wearing Considerations: Due to its cleavage and hardness, tanzanite should be handled with care. It is advisable to put on tanzanite jewelry after applying cosmetics, hairsprays, and perfumes, as these substances can leave a film that dulls the stone’s luster. Remove rings and bracelets before engaging in physical activities, household chores, or any task that could involve impact or abrasion. For daily wear, tanzanite is best suited for earrings or pendants, which are less likely to receive knocks than rings.
Professional Check-ups: For valuable tanzanite jewelry, periodic inspection by a professional jeweler is recommended. They can check the security of the setting, clean the stone professionally, and address any minor wear on the prongs or settings that could compromise the stone’s safety.
Conclusion
Tanzanite stands as a testament to the dynamic nature of the gemstone world, where new discoveries can capture the global imagination within a single generation. As a December birthstone, it offers a modern, vibrant alternative to the traditional turquoise and zircon, distinguished by its unique pleochroic colors and singular geographic origin. Its journey from a chance discovery in Tanzania to a celebrated gem in the international market underscores the interplay of geology, commerce, and culture.
While its history lacks the ancient lore of other birthstones, its gemological properties—particularly its captivating color range and the critical need for careful handling—define its character and value. For those born in December, tanzanite is more than a birthstone; it is a symbol of rarity and transformation, a gem whose beauty is deeply tied to the specific geological conditions of one corner of the world. Whether chosen for its aesthetic appeal, its symbolic meaning, or its status as a modern classic, tanzanite continues to fascinate and inspire, securing its place in the pantheon of cherished gemstones.