Tanzanite, also known as Zoisite or Danquan Stone, is a mesmerizing gemstone that has captured the hearts of jewelry enthusiasts and collectors worldwide. Its unique purple-blue hue, coupled with its rarity and fascinating discovery story, makes it a true gem of legend. This article aims to provide a detailed and scientifically grounded introduction to tanzanite, shedding light on its origins, physical properties, and the reasons behind its growing popularity.
Origins and Discovery
The story of tanzanite begins in the lush landscapes of Tanzania, a country located on the continent of Africa. Tanzania is renowned for its diverse wildlife and stunning natural scenery, including the iconic Mount Kilimanjaro, the highest mountain in Africa. The gemstone tanzanite was first discovered in 1967 near the foot of this majestic mountain, in the Arusha region.
The discovery of tanzanite is said to have been a serendipitous event. Local inhabitants noticed that a grassland fire had transformed yellow stones into a striking blue color. They shared these mysterious, blue-purple crystals with Portuguese geologist Manuel D’Souza, who was traveling in the Merelani area. Recognizing the uniqueness of these crystals, D’Souza assisted in introducing this gemstone to the world, particularly through the efforts of Tiffany & Co. in New York.
Naming and Popularization
In 1968, Tiffany & Co. decided to name this new gemstone “Tanzanite,” in honor of the country of its discovery and the newly formed United Republic of Tanzania. The name has stuck, and tanzanite has become synonymous with elegance and rarity. Foreign collectors and jewelers refer to it as “Danquan Stone,” reflecting its global appeal.
Tiffany & Co. played a pivotal role in bringing tanzanite to the international jewelry market. The company recognized the potential of this gemstone and actively promoted it, showcasing its beauty and uniqueness. American women, particularly those who appreciate novelty, quickly adopted tanzanite as a favorite. Since then, its popularity has continued to grow, and it is now recognized as a gemstone of significance and value.
Physical Properties and Characteristics
Tanzanite is a silicate mineral belonging to the zoisite group. Its chemical composition is Ca2Al3(SiO4)3(OH), making it a calcium aluminum silicate hydroxide. This gemstone crystallizes in the orthorhombic crystal system, with a hardness of 6.5 to 7 on the Mohs scale. Its density is approximately 3.35g/cm³, and its refractive index ranges from 1.697 to 1.700, with a birefringence of 0.008-0.013.
Tanzanite’s most striking feature is its color. Its natural color can range from blue-green with brown tones to gray, brown, yellow, green, and light pink. However, the most sought-after tanzanite gems exhibit a deep, captivating blue-purple hue, reminiscent of the twilight skies over Tanzania. This color is often enhanced through heat treatment, a process that stabilizes the color and is internationally recognized within the gemstone industry.
Under certain lighting conditions, tanzanite displays a phenomenon known as pleochroism, where it appears to change color depending on the viewing angle. This property adds to its mystical charm and enhances its appeal as a gemstone.
Geological Occurrence and Mining
The occurrence of gem-quality tanzanite is exceptionally rare. To date, the only known commercial source of tanzanite is a small, 8-kilometer-long, 2-kilometer-wide area near the Merelani Hills in the Arusha region of Tanzania. This limited range makes tanzanite one of the rarest gemstones in the world.
Tanzanite forms as a result of regional metamorphism and hydrothermal alteration. It is found within metamorphic rocks, marble, and schist associated with the Mozambique Belt. Mining for tanzanite is challenging due to the harsh conditions and the need for specialized techniques to extract the gemstones from their host rocks.
Unfortunately, the mining of tanzanite in Tanzania has faced numerous challenges. The country lacks a mature gemstone market, and the mining industry is often plagued by disorderly mining practices, which have caused significant damage to the deposits. Furthermore, only a few countries, such as the UK and India, possess advanced processing technology for tanzanite, which limits the quality and export potential of locally processed gems.
Jewelry and Investment Potential
Despite these challenges, tanzanite has continued to gain popularity in the jewelry industry. Its unique color and rare occurrence make it a highly desirable gemstone for jewelry creation. From exquisite rings and pendants to elegant earrings and bracelets, tanzanite adds a touch of sophistication and elegance to any piece of jewelry.
In addition to its aesthetic appeal, tanzanite also holds investment potential. Due to its rarity and increasing demand, the price of tanzanite has been steadily rising over the years. Gem-quality tanzanite is becoming increasingly scarce, with geological estimates suggesting that it may be depleted by 2020. This scarcity, coupled with the gemstone’s growing popularity, has led to a surge in its value, making it a sought-after investment option for collectors and investors.
Distinguishing Tanzanite from Other Gemstones
While tanzanite’s unique color and appearance make it easy to distinguish from many other gemstones, it can sometimes be mistaken for similar-looking gems, such as blue sapphire and iolite. However, there are several key differences that can help in identifying tanzanite.
Firstly, tanzanite’s pleochroism is a distinctive feature that sets it apart from other gemstones. When viewed under a dichroic scope, tanzanite will display three distinct colors: blue, purple, and gray-black. Secondly, tanzanite’s refractive index and density differ from those of blue sapphire and iolite, allowing gemologists to distinguish it using specialized equipment.
Synthetic gemstones that mimic the appearance of tanzanite have not yet been successfully produced. However, there are synthetic spinels, synthetic corundum, and other synthetic gemstones that are used as imitations. It is crucial to purchase tanzanite from reputable sources and to have it examined by a qualified gemologist to ensure its authenticity.
Preservation and Sustainability
The preservation and sustainability of tanzanite resources are critical issues that require attention. With the depletion of gem-quality tanzanite deposits, it is essential to adopt responsible mining practices to ensure the long-term availability of this gemstone.
The Tanzanian government has taken steps to address the challenges faced by the tanzanite mining industry. It has implemented measures to protect mining areas and control illegal trading, although the lack of funding and infrastructure poses significant challenges. Collaboration between the government, mining companies, and the gemstone industry is crucial to ensure the sustainable development of tanzanite resources.
Conclusion
In conclusion, tanzanite is a rare and enchanting gemstone that has captured the imagination of jewelers, collectors, and enthusiasts worldwide. Its unique color, rare occurrence, and fascinating discovery story make it a true gem of legend. While challenges remain in the mining and processing of tanzanite, its popularity and investment potential continue to grow, making it a valuable addition to any jewelry collection or investment portfolio.
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