Introduction
The gemstone designated for those born on December 7th is Tanzanite, a vibrant, pleochroic gem renowned for its rich violet-blue hues. First discovered in the 20th century, it is one of the youngest members of the modern birthstone calendar, having been officially recognized by the American Gem Trade Association (AGTA) in 2002. Its significance extends beyond its striking color; it is deeply intertwined with themes of transformation, spiritual insight, and wisdom. This article explores the history, geological origins, gemological properties, and symbolic meanings of Tanzanite, drawing exclusively from authoritative sources to provide a comprehensive guide for enthusiasts, collectors, and students of gemology.
History and Lore
The tradition of associating specific gemstones with birth dates is ancient, with roots in the biblical High Priest’s breastplate, which featured twelve stones representing the twelve tribes of Israel and the twelve months of the year. This concept evolved over centuries, eventually leading to the modern birthstone lists used today. While traditional December birthstones like Turquoise and Zircon have histories spanning millennia, Tanzanite is a distinctly contemporary addition.
Tanzanite’s history is remarkably brief. It was first identified in the Merelani Hills of Northern Tanzania in the 1960s. Its discovery is often attributed to a Masai herder who noticed the gem’s brilliant blue crystals in the late 1960s. However, the gemstone’s journey from a local curiosity to a globally recognized birthstone was catalyzed by the efforts of the jewelry company Tiffany & Co., which recognized its potential and launched a marketing campaign in 1968. The company named the stone after its country of origin, Tanzania.
In 2002, the American Gem Trade Association (AGTA) officially added Tanzanite to the list of birthstones for December. This decision was made to offer a modern, vibrant alternative to the traditional stones. While sources do not provide specific ancient mythological narratives directly tied to Tanzanite—likely due to its recent discovery—the gemstone has quickly developed its own lore. It is often associated with themes of new beginnings and transformation, reflecting its recent entry into the gemological world and its unique geological formation.
Geological Formation and Sources
Tanzanite is a variety of the mineral zoisite, specifically the blue to violet-blue variety colored by trace amounts of vanadium. Its formation is a geological rarity, making it one of the most exclusive gemstones in the world.
Geological Formation: Tanzanite is formed through a specific and unusual geological process. The Merelani Hills, the sole source of gem-quality Tanzanite, are part of the East African Rift system. The gem forms in the presence of high heat and pressure, which transforms the mineral zoisite from its common green color to the prized blue-violet hue. This process is believed to have occurred approximately 585 million years ago during the Neoproterozoic Era. The specific conditions required for this color change are so unique that geologists consider the Merelani deposits to be the only known source of this gem, leading to the belief that Tanzanite is 1,000 times rarer than diamond.
Mining Locations: As noted, all commercially viable Tanzanite deposits are located in a small, four-square-kilometer area in the Merelani Hills of Northern Tanzania, near the base of Mount Kilimanjaro. The mining area is divided into blocks, with Block A being the most famous and productive. The limited geographic origin contributes significantly to the stone's value and allure. While zoisite is found in other parts of the world, the specific blue-violet variety known as Tanzanite is exclusive to this region.
Gemological Properties
Tanzanite is prized for its remarkable color, but its other gemological characteristics are equally important for identification, valuation, and care.
Color: The most defining characteristic of Tanzanite is its color. It exhibits a pleochroic property, meaning it displays different colors when viewed from different crystal directions. Typically, it shows blue, violet, and burgundy red. The primary color range is a rich, violet-blue, often described as "velvety." The intensity of the blue is influenced by the concentration of vanadium and the heat treatment it undergoes. While natural, unheated Tanzanite can be brownish, virtually all commercial Tanzanite is heat-treated to enhance its blue and violet colors, a stable and accepted industry practice.
Hardness and Durability: On the Mohs scale of hardness, Tanzanite ranks between 6 and 7. This makes it relatively durable for everyday wear but susceptible to scratching if not handled with care. It is softer than quartz (7) and significantly softer than diamond (10) or corundum (9). Its toughness is fair to good, but it possesses perfect cleavage in one direction, meaning it can split if struck with force along that plane. This property necessitates careful handling and setting in protective jewelry designs.
Chemical Composition: Tanzanite is a variety of zoisite, with the chemical formula Ca₂Al₃(SiO₄)₃(OH). The blue color is induced by trace amounts of vanadium (V) substituting for aluminum in the crystal lattice. The presence of iron and chromium can also influence the final hue, contributing to the stone's complex color profile.
Refractive Index and Specific Gravity: Tanzanite has a refractive index ranging from 1.691 to 1.700, with a birefringence of 0.008 to 0.013. Its specific gravity typically falls between 3.35 and 3.38. These properties are standard for zoisite and are used in gemological laboratories to confirm the identity of the stone, especially when distinguishing it from similar-looking materials like synthetic sapphire or glass.
Clarity and Inclusions: Tanzanite is often clean to the eye, but it can contain inclusions such as fingerprints, needles, or minute crystals. Unlike some gemstones where inclusions are prized (like emeralds), inclusions in Tanzanite can affect its clarity and value. High-quality Tanzanite is characterized by excellent clarity and a deep, saturated color.
Gemological Data Summary
The following table summarizes key gemological properties of Tanzanite as derived from standard gemological sources.
| Property | Details |
|---|---|
| Mineral Family | Zoisite (Group: Epidote) |
| Chemical Formula | Ca₂Al₃(SiO₄)₃(OH) |
| Color | Blue to violet-blue, often pleochroic (blue, violet, burgundy) |
| Mohs Hardness | 6 - 7 |
| Crystal System | Orthorhombic |
| Refractive Index | 1.691 - 1.700 |
| Specific Gravity | 3.35 - 3.38 |
| Birefringence | 0.008 - 0.013 |
| Origin | Merelani Hills, Tanzania (sole source for gem quality) |
Symbolism and Metaphysical Beliefs
While Tanzanite lacks the ancient historical lore of stones like turquoise or amethyst, it has rapidly accumulated a rich tapestry of modern symbolism and metaphysical beliefs. These associations are largely contemporary, stemming from its discovery and marketing in the late 20th century.
Transformation and New Beginnings: A central theme in Tanzanite’s symbolism is transformation. This is linked to its geological history—being formed under intense heat and pressure—and its recent discovery, which transformed a local mineral into a global gemstone. It is often associated with new beginnings, making it a powerful symbol for those seeking change or embarking on a new life chapter. For individuals born on December 7th, it is believed to encourage personal growth and the courage to embrace transformation.
Spiritual Insight and Wisdom: Tanzanite is frequently linked to spiritual awareness and higher consciousness. Its deep blue and violet hues are associated with the third eye and crown chakras in various spiritual traditions. It is believed to facilitate a connection to higher realms, enhance intuition, and promote clarity of thought. This makes it a popular stone for meditation and those seeking deeper spiritual understanding.
Communication and Clarity: Another attributed property is the enhancement of communication. It is said to help articulate thoughts and feelings clearly, bridging the gap between the heart and the mind. This symbolism aligns with its association with wisdom and insight, suggesting that those who wear it may find it easier to express complex ideas and emotions.
December 7th Specific Significance: For those born on December 7th, Tanzanite is said to embody specific traits. It is believed to endow its bearers with wisdom, intuition, and a profound understanding of themselves and others. The gemstone serves as a personal talisman, reflecting the individual’s inner depth and spiritual potential.
Jewelry and Market Value
Tanzanite’s vibrant color and relative rarity make it a sought-after gemstone in jewelry design. Its value is influenced by several factors, including color, clarity, cut, and carat weight.
Color as the Primary Value Factor: The most critical factor in determining Tanzanite’s value is its color. The most prized hues are the deep, vivid violet-blue to pure blue shades. Lighter, less saturated stones are more common and less valuable. The secondary color (burgundy or purple) can also affect value; stones with a strong, even blue color without a muddy or overly brownish secondary hue command the highest prices. The phenomenon of pleochroism is often considered an asset, as it adds depth and complexity to the stone's appearance.
Cut and Carat Weight: Tanzanite is cut into a variety of shapes to maximize color and minimize weight loss from the rough. Common cuts include oval, cushion, pear, and round. Due to its perfect cleavage, cutters must exercise great skill to avoid splitting the stone during faceting. Larger stones (over 5 carats) are rarer and more valuable per carat, assuming color and clarity remain high.
Market Value and Rarity: As noted, Tanzanite is mined in a very small area, contributing to its rarity and value. High-quality, large Tanzanite stones can command significant prices, comparable to other fine blue gemstones. However, it is generally more affordable than sapphire of comparable quality. The market value is also influenced by its status as a birthstone, which has increased demand, particularly for jewelry pieces designed for December birthdays.
Jewelry Designs: Tanzanite is versatile and is set in a wide range of jewelry, from delicate rings and earrings to bold statement necklaces and pendants. Its color pairs well with both yellow and white metals, and it is often accentuated with diamonds to enhance its brilliance. Traditional designs often feature a single, prominent Tanzanite as a solitaire, while contemporary styles may incorporate Tanzanite into more complex, multi-stone settings.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of Tanzanite jewelry, given its moderate hardness and perfect cleavage.
Cleaning: The safest method for cleaning Tanzanite is with warm, soapy water and a soft brush. Ultrasonic cleaners and steam cleaners should be avoided, as the vibrations and heat can potentially damage the stone, especially if it has inclusions or fractures. After cleaning, rinse thoroughly and dry with a soft, lint-free cloth.
Storage: To prevent scratching, Tanzanite should be stored separately from other jewelry pieces. A soft pouch or a lined jewelry box is ideal. It is also advisable to avoid exposing Tanzanite to sudden temperature changes, which could potentially cause thermal shock.
Handling and Wear: Given its cleavage, Tanzanite should be protected from hard blows. It is recommended to remove Tanzanite jewelry before engaging in physical activities, gardening, or heavy household chores. For rings, which are most prone to impact, consider protective settings like bezels or halo designs that shield the stone.
Chemical Exposure: Avoid exposing Tanzanite to harsh chemicals, including household cleaners, chlorine, and acids, which can damage the stone's surface or alter its color. It is best to put on jewelry after applying cosmetics, perfumes, and hairsprays.
Conclusion
Tanzanite, the birthstone for December 7th, is a gemstone of remarkable beauty and significance. Its journey from the slopes of Mount Kilimanjaro to the international jewelry market is a modern gemological tale. With its captivating violet-blue color, unique pleochroic properties, and symbolic associations with transformation and wisdom, Tanzanite offers a distinct and meaningful choice for those born in December. While its hardness requires careful handling, its unparalleled color and rarity ensure its place as a cherished gemstone in the world of fine jewelry. For individuals born on December 7th, it serves as a personal emblem of insight, clarity, and the profound beauty found in new beginnings.