Tanzanite: The Captivating Blue Birthstone of December

Tanzanite, a gemstone renowned for its mesmerizing violet-blue to bluish-purple hues, stands as one of the most significant modern additions to the birthstone calendar. Designated as a birthstone for the month of December in 2002, this rare gemstone is prized for its unique color-changing properties and compelling backstory. Unlike many traditional birthstones with ancient histories, tanzanite’s tale is one of recent discovery and rapid global fame. This article provides a comprehensive exploration of tanzanite, drawing from gemological data and historical records to detail its formation, properties, symbolism, and its journey to becoming a cherished December birthstone.

The gemstone’s narrative begins with its geological uniqueness and extends through its cultural adoption, offering a fascinating case study in modern gemology. Its journey from a newly discovered mineral to a celebrated birthstone highlights the dynamic nature of the gem trade and the evolving traditions of jewelry. We will examine its physical characteristics, the science behind its captivating color, its limited geographic origin, and the practical considerations for its care and use in jewelry. By delving into these aspects, we can appreciate why tanzanite has captured the imagination of gem enthusiasts and jewelry buyers worldwide.

History and Lore

The history of tanzanite is remarkably brief, which sets it apart from many other gemstones that have been valued for millennia. The gemstone was first discovered in the 1960s in the country of Tanzania, from which it derives its name. This geographical origin is a key part of its identity, as tanzanite is found in only one location on Earth, making it significantly rarer than diamonds. The initial discovery led to its identification as a blue variety of the mineral zoisite. The trade name "tanzanite" was later popularized by the luxury jewelry company Tiffany & Co., which recognized the gem’s potential and began marketing it in the late 1960s. This strategic branding was instrumental in propelling tanzanite from a mineralogical curiosity to a sought-after gemstone in the international market.

The inclusion of tanzanite as a December birthstone is a relatively recent development in the long history of birthstone traditions. The practice of assigning specific gems to birth months originated in eighteenth-century Europe and spread to the United States. In the United States, the tradition was formalized in 1912 when the American National Retail Jeweler’s Association (now known as Jewelers of America) adopted a standardized list of monthly birthstones. This list was periodically updated to reflect market trends and the availability of new gems. In 2002, the modern birthstone list was amended to include tanzanite for December, alongside traditional birthstones like zircon and turquoise. This addition acknowledged the gemstone’s growing popularity and its unique aesthetic appeal, offering December-born individuals a vibrant blue-violet alternative.

The lore surrounding tanzanite is primarily rooted in its modern discovery and lacks the ancient superstitions and legends associated with older gemstones. Its cultural significance is tied to its place of origin and its rapid rise to prominence in the 20th century. As a product of a specific geological event in a single location, its story is one of modernity and exclusivity. While it does not have centuries of folklore, its narrative is compelling, speaking to rarity, natural beauty, and the power of effective marketing in shaping contemporary gemstone traditions.

Geological Formation and Sources

Tanzanite’s geological story is as unique as its color. It is a variety of the mineral zoisite, specifically the blue to violet-blue form. The gemstone’s formation is the result of a rare geological event. According to geological studies, the tanzanite deposits are found in the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. This area is the world’s only known source of gem-quality tanzanite. The mineral was formed approximately 585 million years ago during a massive metamorphic event, where intense heat and pressure altered the original rock formations, creating the conditions necessary for zoisite crystals to develop.

The rarity of tanzanite is directly linked to this singular point of origin. Unlike many gemstones that are mined in multiple countries, tanzanite’s geographic confinement to a small area of Tanzania makes it hundreds of times rarer than diamond. This extreme rarity is a major factor in its value and appeal. The mining process itself is challenging, often involving small-scale operations that extract the rough crystals from the earth.

The color of tanzanite is a critical aspect of its geological identity. Most tanzanite sold in jewelry today has undergone a heat treatment process to achieve its characteristic blue to bluish-purple to bluish-violet color. In its natural state, zoisite is typically brownish or greenish. The heat treatment, which involves exposing the rough stone to controlled temperatures, permanently alters the crystal structure to remove the brownish tones and enhance the desirable blue and violet hues. This process is standard in the industry and is considered acceptable as long as it is properly disclosed to consumers. The heat treatment is not a form of artificial coloring but a permanent enhancement that reveals the stone’s inherent potential for color.

Gemological Properties

Tanzanite possesses a distinct set of physical and optical properties that define its character and inform its use in jewelry. Understanding these properties is essential for gemologists, jewelers, and consumers alike, as they directly impact the stone’s durability, appearance, and care requirements.

Color and Optical Phenomena: The most celebrated property of tanzanite is its color. It exhibits a range of hues from a pure, deep blue to a vivid violet-blue, often with a bluish-purple secondary hue. A notable optical characteristic is its pleochroism, a phenomenon where a gemstone displays different colors when viewed from different crystal directions. In tanzanite, this results in a color shift from violet-blue to bluish-purple to a reddish-violet depending on the angle of viewing. This dynamic quality adds depth and interest to the stone, making it particularly captivating in well-cut gems.

Hardness and Durability: On the Mohs scale of mineral hardness, tanzanite has a rating of 6.5 to 7. While this is adequate for many types of jewelry, it places tanzanite in the "Fair to Poor" category for durability in certain settings. Gems with a hardness below 7.5 are more susceptible to scratching and abrasion from everyday materials like dust (which contains quartz, hardness 7) and other gemstones. Therefore, while tanzanite can be worn in earrings and pendants where it is less likely to receive impacts, it requires caution in rings and bracelets. A protective mounting is recommended for tanzanite jewelry worn on the hand, and it is advisable to remove such pieces during activities that could subject them to hard knocks or abrasion.

Cleavage and Toughness: Tanzanite has perfect cleavage in one direction. Cleavage is the tendency of a mineral to break along flat planes of weakness in its crystal structure. Perfect cleavage means the stone can be split cleanly along these planes with relatively little force. This property makes tanzanite vulnerable to breakage if struck with force at the right angle. Its toughness, or resistance to breakage, is therefore considered fair to poor. This is a critical factor for jewelers when designing settings; the stone must be placed in a setting that protects its edges and corners from impact.

Chemical Composition and Crystal System: Chemically, tanzanite is a calcium aluminum hydroxyl silicate, with the formula Ca₂Al₃(SiO₄)₃(OH). It crystallizes in the orthorhombic crystal system. Its refractive index ranges from 1.691 to 1.700, and it has a specific gravity of 3.35. These properties are used by gemologists to identify tanzanite and distinguish it from other blue gemstones like sapphire or aquamarine.

The following table summarizes key gemological properties of tanzanite:

Symbolism and Metaphysical Beliefs

While tanzanite lacks the ancient mythological associations of gemstones like ruby or sapphire, it has accrued a layer of modern symbolism and metaphysical beliefs, largely driven by its unique properties and recent discovery. Its symbolism is often tied to its transformative color and its rarity.

The most prominent symbolic association for tanzanite is its connection to transformation and spiritual awakening. This belief stems from the gemstone’s own geological story—its creation through intense heat and pressure—and its remarkable color change when viewed from different angles. Enthusiasts of crystal healing and metaphysical practices often attribute to tanzanite the ability to facilitate higher consciousness, intuition, and psychic abilities. It is sometimes called the "stone of intuition" or the "stone of transformation," believed to help individuals connect with their spiritual guides and navigate life changes with clarity and purpose.

The gemstone’s blue and violet hues are also linked to the throat and brow (third eye) chakras in certain belief systems. The blue component is associated with communication and self-expression, while the violet is linked to intuition and spiritual insight. Therefore, tanzanite is sometimes used in meditation or worn as a talisman to enhance communication with the divine or to unlock inner wisdom.

It is important to note that these metaphysical beliefs are not supported by scientific evidence and fall outside the realm of gemology. They are part of the cultural and personal significance that individuals ascribe to the stone. As with many gemstones, the symbolism of tanzanite is a blend of its physical characteristics and the narratives built around it by its admirers. For many wearers, the primary meaning of tanzanite is its beauty, rarity, and its status as a modern birthstone, representing a personal connection to the month of December.

Care and Cleaning

Proper care is essential to maintain the beauty and integrity of tanzanite jewelry, given its moderate hardness and perfect cleavage. Understanding its physical limitations allows owners to enjoy their gems for decades with appropriate handling and maintenance.

Cleaning Methods: The safest way to clean tanzanite is with warm water, a mild dish soap, and a soft brush, such as a toothbrush with soft bristles. Gently scrub the stone and its setting to remove oils, lotions, and dirt. Rinse thoroughly with clean water to remove any soap residue, and dry with a soft, lint-free cloth. It is crucial to avoid ultrasonic cleaners and steam cleaners. The vibrations from an ultrasonic cleaner can cause internal fractures in tanzanite to worsen, potentially leading to breakage. Similarly, the high heat and pressure from steam cleaners can damage the stone or its setting.

Storage and Handling: When not being worn, tanzanite jewelry should be stored separately from other jewelry pieces to prevent scratching. It is best kept in a soft-lined jewelry box or a fabric pouch. Due to its perfect cleavage, tanzanite should never be subjected to hard blows or sharp impacts. Owners should remove tanzanite rings and bracelets before engaging in activities such as gardening, sports, or heavy manual work where the stone could be struck against a hard surface.

Professional Inspection: It is advisable to have tanzanite jewelry inspected by a professional jeweler periodically, especially if it is set in a ring or bracelet. The jeweler can check the security of the setting, ensuring that the prongs are tight and that the stone is not at risk of falling out. This is particularly important for tanzanite due to its cleavage; a loose stone is more likely to be damaged if it is knocked.

By following these care guidelines, owners can ensure that their tanzanite remains vibrant and intact. The gemstone’s unique color and rarity make it a treasured possession, and with proper care, it can be a lasting part of a jewelry collection.

Conclusion

Tanzanite’s journey from a newly discovered mineral in the 1960s to a designated December birthstone in 2002 exemplifies the dynamic evolution of gemstone traditions. Its singular geographic origin in Tanzania contributes to its extreme rarity and compelling narrative, while its distinctive violet-blue color and pleochroic qualities make it a standout in the world of colored gemstones. As a modern birthstone, it offers December-born individuals a gemstone that is both visually striking and rich with contemporary symbolism, often associated with transformation and spiritual insight.

From a gemological perspective, tanzanite’s properties present both opportunities and considerations for jewelry use. Its hardness of 6.5 to 7 makes it suitable for certain jewelry types, but its perfect cleavage and fair toughness necessitate careful handling and protective settings, particularly for rings and bracelets. The standard heat treatment used to enhance its color is a well-established and accepted practice in the industry, provided it is properly disclosed.

Ultimately, tanzanite’s significance lies in its unique combination of beauty, rarity, and modern lore. It stands as a testament to how new discoveries can enrich long-standing traditions, offering a fresh perspective on the enduring human fascination with precious stones. For gemstone enthusiasts, jewelry buyers, and students of gemology, tanzanite represents a fascinating case study in geology, market forces, and cultural adoption, solidifying its place as a cherished gemstone in the 21st century.

Sources

1. Geology.com - Birthstones
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3. Gems in Myth, Legend and Lore by Bruce G. (Note: The provided source citation in the text refers to this publication, though the specific URL is not provided in the source list.)
4. Jewelers of America - Birthstone Jewelry (Note: The provided source citation in the text refers to this organization, though the specific URL is not provided in the source list.)