December 21 represents a pivotal moment in the calendar, marking the winter solstice and the transition from the zodiac sign of Sagittarius to the disciplined ambition of Capricorn. For individuals born on this specific day, the designated birthstone is tanzanite, a gem of extraordinary rarity and captivating color. Unlike ancient stones that have been known for millennia, tanzanite is a distinctly modern discovery, having only entered the gemological lexicon in the latter half of the 20th century. Despite its youth, it has rapidly ascended the ranks to become one of the most sought-after blue gems in the world, prized for its deep blue-violet hues and unique geological origin.
Tanzanite stands out not only for its beauty but also for its singular source. Found in a microscopic area of the Merelani Hills of Northern Tanzania, it is rarer than diamond. Its association with the Capricorn sign aligns its transformative energy with the sign’s traits of ambition and practicality. This article explores the comprehensive history, geological formation, gemological properties, and symbolism of tanzanite, drawing upon expert analysis to provide a complete profile of this remarkable December birthstone.
History and Lore
The history of tanzanite is exceptionally brief compared to other gemstones, which lends it a unique allure. It is one of the few gemstones to emerge in the modern era, with its discovery dated to 1967 in Tanzania. This recent origin means that tanzanite lacks the deep, ancient folklore associated with stones like sapphire or emerald. However, its rapid integration into the modern jewelry industry has created its own legacy.
The Modern Discovery
The gemstone was originally identified as a variety of the mineral zoisite. Its discovery is attributed to Manuel de Souza, a Tanzanian tailor and prospector, who found transparent blue crystals in the Merelani Hills. Initially, the stone was marketed under various names, including "blue zoisite," but the name was changed to "tanzanite" by Tiffany & Co. in 1968 to honor its country of origin and differentiate it from other blue stones. The jewelry giant recognized the gem's potential and introduced it to the market, promoting it as "the most beautiful blue gemstone to be discovered in 2,000 years."
Integration into Zodiac Tradition
While the stone itself is new, its adoption into zodiac traditions was swift. For those born on December 21, tanzanite is recognized as the birthstone associated with the entry into Capricorn. Capricorn is a zodiac sign characterized by ambition, determination, and practicality. The deep, introspective color of tanzanite is believed to support the Capricorn’s drive for success and personal growth. The stone’s associations with transformation and spiritual development resonate with the Capricorn’s desire to evolve and achieve goals.
Although tanzanite itself is a modern discovery, its color evokes the same sense of majesty and mystery as sapphires and amethysts, which have been revered for centuries. In ancient times, deep blue and violet gemstones were often associated with royalty and divine power. Today, tanzanite is frequently used in high-end jewelry and is considered a symbol of luxury and sophistication.
Geological Formation and Sources
The geological story of tanzanite is as unique as its appearance. It is a variety of the mineral zoisite, which belongs to the epidote group of minerals. The conditions required to form tanzanite are so specific that the gem is believed to have been created only once in the history of the planet.
Formation and Rarity
Tanzanite owes its existence to a unique set of geological circumstances. Roughly 585 million years ago, the precursor to the gem, the mineral zoisite, was formed during the metamorphism of the rocks in Tanzania. However, the intense heat required to transform the brownish zoisite into the vivid blue-violet variety occurred much later, likely due to a tectonic event or contact metamorphism from a large igneous intrusion. This event subjected the zoisite to temperatures of around 600 degrees Celsius, which altered its chemical structure and introduced the trace element vanadium, responsible for its signature color.
This specific geological event occurred in a very small area—roughly four kilometers by two kilometers—in the Merelani Hills of the Manyara Region in Northern Tanzania. This is the only known commercial source of tanzanite in the world. The mining area is divided into four blocks, with Block C being the most productive. The extreme rarity of the formation conditions explains why tanzanite is found in only one location on Earth, making it geologically rarer than diamond.
Mining and Production
Tanzanite is mined using both open-pit and underground methods. The mining operations are often small-scale, and the recovery of gem-quality material is challenging. The stones are typically found in three forms: as rough crystals, in matrix (attached to the host rock), or as tumbled fragments. Because of the limited mining area and the finite nature of the deposit, the supply of tanzanite is strictly limited. This scarcity drives its value and makes it a prized possession for collectors and investors alike.
Gemological Properties
Tanzanite possesses a set of physical and optical properties that make it a standout in the gemological world. While it is relatively soft compared to some traditional gemstones, its visual impact is unmatched.
Color and Pleochroism
The most defining characteristic of tanzanite is its color. It ranges from a pure, ultramarine blue to a vibrant violet, with the most valuable stones exhibiting a deep, rich blue with a distinct violet undertone. The color is the result of vanadium trace elements within the crystal structure. When the stone is heated, the vanadium is oxidized, which removes the brownish overtones and reveals the saturated blue-violet hue.
Tanzanite is strongly pleochroic, meaning it displays different colors when viewed from different crystal directions. It typically exhibits trichroism, showing blue, violet, and reddish-brown colors depending on the orientation. This property requires a skilled cutter to orient the rough stone to display the most desirable blue-violet face-up color, minimizing the visibility of the reddish-brown axis.
Hardness and Durability
On the Mohs scale of hardness, tanzanite ranks between 6 and 6.5. This makes it a relatively soft gemstone compared to diamond (10), sapphire (9), or even blue topaz (8). Because of its lower hardness, tanzanite is more susceptible to scratching and abrasion. It also possesses distinct cleavage, meaning it can split along certain planes if struck with force. These properties necessitate careful handling and protective settings, particularly for rings or bracelets that are exposed to daily wear.
Refractive Index and Specific Gravity
Tanzanite has a refractive index that typically falls between 1.690 and 1.700, with a birefringence of 0.008 to 0.013. Its specific gravity ranges from 3.35 to 3.38. These figures are standard for the zoisite mineral group and help gemologists distinguish tanzanite from other blue stones like sapphire or iolite.
Treatment and Clarity
Almost all tanzanite on the market has been heat-treated to enhance its color. This treatment is stable and permanent and is generally accepted within the industry. Natural, unheated tanzanite is exceptionally rare. In terms of clarity, tanzanite is typically "eye-clean," meaning inclusions are not visible to the naked eye. However, some stones may contain needle-like inclusions or fluid fingerprints, which can affect transparency.
Symbolism and Metaphysical Beliefs
Although tanzanite is a modern stone, it has quickly accumulated a rich tapestry of metaphysical associations. Its properties are often linked to its color, rarity, and the zodiac sign of Capricorn.
Transformation and Spiritual Growth
The primary metaphysical association of tanzanite is transformation. Given its formation under intense heat and pressure, and its ability to change color when heated, it is viewed as a stone that facilitates change and evolution. It is believed to aid in the transition from one state of being to another, making it a powerful tool for those undergoing personal or spiritual growth.
For Capricorns born on December 21, tanzanite is said to enhance the sign’s natural discipline and ambition while encouraging a deeper connection to intuition and spiritual purpose. It is often used in meditation to open the crown chakra and facilitate communication with higher realms.
Creativity and Intuition
Tanzanite is also associated with the stimulation of creativity and the awakening of intuition. It is believed to harmonize the mind and heart, allowing for clearer expression of ideas and emotions. Some practitioners suggest that tanzanite can help overcome resistance to change, encouraging the wearer to embrace new opportunities with confidence.
Connection to the Throat Chakra
Due to its blue color, tanzanite is frequently linked to the throat chakra, which governs communication and self-expression. It is believed to encourage truthfulness and clarity in speech, making it a beneficial stone for public speakers, teachers, and those in leadership roles.
Care and Cleaning
Given its relative softness and cleavage, tanzanite requires specific care to maintain its beauty and integrity.
Safe Storage and Handling
Because tanzanite ranks 6 to 6.5 on the Mohs scale, it should be stored separately from harder gemstones to prevent scratching. It is advisable to keep tanzanite jewelry in a soft cloth pouch or a lined jewelry box. When not being worn, it should be kept away from direct sunlight, as prolonged exposure to heat and light can potentially cause fading, although the heat treatment used to enhance the color is permanent.
Cleaning Methods
Tanzanite should be cleaned using warm water, a mild soap, and a soft brush. Ultrasonic cleaners and steam cleaners are strictly discouraged, as the vibrations and heat can cause damage or exacerbate existing cleavage planes. After cleaning, the stone should be dried with a soft, lint-free cloth. It is important to avoid harsh chemicals, including bleach and ammonia, which can damage the surface of the gem.
Protective Settings
Due to its cleavage and lower hardness, tanzanite is best suited for jewelry that is not subjected to hard knocks, such as pendants, earrings, and brooches. If used in rings, it should be set in a protective mounting, such as a bezel or halo setting, which safeguards the edges of the stone from impact.
Conclusion
Tanzanite is a gemstone of unparalleled rarity, found only in a specific region of Tanzania, and represents a significant addition to the list of December birthstones. Its discovery in the 20th century brought a new spectrum of blue-violet beauty to the gemological world, quickly capturing the attention of jewelers and collectors. For those born on December 21, it serves as a powerful symbol of transformation and ambition, aligning perfectly with the traits of the Capricorn zodiac sign.
Its unique geological formation, distinct pleochroic properties, and symbolic associations with spiritual growth and creativity make it a fascinating subject of study and admiration. While it requires careful handling due to its physical properties, its visual impact and rarity ensure that tanzanite remains a treasured gemstone, embodying both the mysteries of the earth and the aspirations of those who wear it.