Tanzanite is a gemstone that has captured the fascination of the jewelry world with its captivating blue-violet hues. To truly understand this remarkable gemstone, it’s essential to explore its origin. Knowing where tanzanite comes from provides insights into its rarity, quality, and the story behind its journey to becoming a prized jewel. In this article, we’ll delve into the details of the geographical location and geological conditions that give birth to tanzanite.
Geographical Origin
The Discovery Location
Tanzanite was first discovered in 1967 in the Merelani Hills, which are located near Mount Kilimanjaro in Tanzania, a country in East Africa. This discovery was quite serendipitous when a Maasai tribesman stumbled upon these beautiful blue-violet crystals while herding his cattle. Since then, the Merelani Hills have become synonymous with tanzanite.
The region is part of the Manyara Region in Tanzania and has since been a focal point for gemstone miners and the jewelry industry interested in sourcing this precious stone.
Exclusive Source
What makes tanzanite truly unique is that, to date, the Merelani Hills remain the only place in the world where significant deposits of tanzanite have been found. Unlike many other gemstones that can be sourced from multiple locations across different countries, tanzanite’s geographical exclusivity adds to its allure and rarity.
This limited origin means that every piece of tanzanite that enters the market can be traced back to this specific area in Tanzania, giving it a special connection to its place of birth.
Geological Setting
The East African Rift System
The Merelani Hills are part of the larger East African Rift System. This is a vast area where the Earth’s crust is being pulled apart by tectonic forces. The rifting creates a dynamic geological environment with intense volcanic and seismic activity.
These forces play a crucial role in the formation of tanzanite as they lead to the creation of fractures and faults in the rocks, allowing for the movement of hot fluids and the introduction of essential chemical elements that will eventually contribute to the crystallization of the gemstone.
Host Rocks
Tanzanite is found within specific types of metamorphic rocks in the Merelani Hills. The main host rocks are amphibolites and schists. Amphibolites are rich in minerals like amphibole and plagioclase feldspar, while schists contain mica and other sheet silicate minerals.
The gemstone crystals grow within these host rocks, often filling small cavities or fractures. The nature of the host rocks influences the growth conditions and can affect the quality and characteristics of the resulting tanzanite gemstones. For example, the chemical composition of the host rocks can interact with the elements involved in tanzanite formation, either facilitating or inhibiting the growth of high-quality crystals.
Formation Process
Role of Magmatic Activity
Magmatic activity deep within the Earth’s mantle near the Merelani Hills region is a key factor in tanzanite’s formation. Magma, which is molten rock, rises from the mantle towards the surface. As it moves through the crust, it brings with it essential chemical elements such as calcium, aluminum, silicon, and oxygen, which are fundamental building blocks for many minerals, including tanzanite.
The interaction of this magma with the surrounding rocks and fluids can also lead to the release of other trace elements like vanadium and chromium, which are responsible for the characteristic color of tanzanite. For instance, vanadium is crucial in imparting the blue and violet hues that make the gemstone so distinctive.
Fluid Migration
Fluids, including hot water and other volatile substances, also migrate through the rocks in the area. These fluids act as carriers for the chemical elements, transporting them to the sites where tanzanite will form. The fluids can dissolve minerals from the surrounding rocks and then deposit the elements in areas where the conditions are right for crystallization.
They can move along fractures and faults in the host rocks, creating channels for the chemical elements to accumulate and react with each other. This fluid migration is an ongoing process that continues over long periods and is essential for the formation of tanzanite.
Crystallization Conditions
Tanzanite crystallizes under specific temperature and pressure conditions. The temperature range is typically between 600 to 800 degrees Celsius, which is relatively high compared to surface temperatures but common for processes occurring deep within the Earth’s crust. The pressure is also significant, equivalent to several thousand times the atmospheric pressure at the Earth’s surface.
These conditions are maintained within the host rocks over an extended period, allowing the chemical elements to arrange themselves in a specific crystal structure. The precise combination of temperature and pressure determines the rate of crystal growth and the quality of the resulting tanzanite crystals.
Mining in the Merelani Hills
Types of Mining Operations
In the Merelani Hills, there are both large-scale commercial mining operations and small-scale, artisanal mining activities. The large mining companies have the resources and equipment to conduct extensive excavation work. They use heavy machinery like drills, crushers, and conveyors to extract the tanzanite-bearing rocks from deep underground.
Artisanal miners, on the other hand, often work in a more traditional and labor-intensive manner. They use hand tools such as picks and shovels to dig through the rocks and may sift through the debris by hand to find the tanzanite crystals. These small-scale miners are usually local individuals or small groups trying to make a living from the gemstone.
Challenges in Mining
Mining tanzanite in the Merelani Hills is not without its difficulties. One major challenge is the depth at which the deposits are located. Miners have to dig down hundreds of feet below the surface in some cases, which requires a lot of time, effort, and resources.
The presence of hard rock formations also poses a problem. These need to be blasted through, which not only slows down the mining process but also presents safety risks to the miners. Additionally, issues like poor ventilation in the mines and the potential for cave-ins are constant concerns that need to be managed.
Impact on the Local Community
The mining of tanzanite has a significant impact on the local community in the Merelani Hills area. It provides employment opportunities for many people, both directly in the mines and in related industries such as gemstone cutting and trading. However, it also brings challenges like environmental degradation due to the mining activities and issues related to the proper management of the industry to ensure fair wages and safe working conditions for the miners.
Tanzanite’s Journey from the Mine to the Market
Extraction and Sorting
Once the tanzanite-bearing rocks are mined, they are taken to processing areas where the gemstones are extracted from the ore. This involves crushing the rocks and using various techniques like gravity separation and sorting to isolate the tanzanite crystals.
Skilled workers then sort the crystals based on their size, quality (including factors like color, clarity, and the potential for cutting), and other characteristics. The best-quality crystals are set aside for use in high-end jewelry, while those of lower quality might be used in more affordable pieces or for industrial purposes.
Gemstone Cutting and Polishing
After sorting, the tanzanite crystals are sent to gemstone cutting studios. Here, expert cutters use specialized tools and techniques to shape the crystals into the desired gemstone cuts, such as oval, round, emerald, or cushion cuts. The cutting process is crucial as it enhances the beauty of the tanzanite by maximizing its color, brilliance, and sparkle.
Polishing is the final step in this transformation, giving the tanzanite a smooth and shiny surface that makes it ready for use in jewelry settings. The cut and polished tanzanite then enters the market, where it is sold to jewelers, collectors, and consumers around the world.
Global Distribution
Jewelry Stores and Retailers
Tanzanite finds its way to jewelry stores all over the world. High-end jewelry chains like Tiffany & Co., Cartier, and Bulgari often feature tanzanite in their collections, showcasing its beauty in elaborate and luxurious designs. These stores source their tanzanite from reliable suppliers who ensure the quality and authenticity of the gemstones.
Local independent jewelry stores also carry tanzanite jewelry, offering a more personalized selection and sometimes focusing on unique or rare pieces. They may have direct connections with gemstone cutters or suppliers in Tanzania, allowing them to offer a diverse range of tanzanite items to their customers.
Gemstone Shows and Exhibitions
Gemstone shows are important platforms for the distribution of tanzanite. Events like the Tucson Gem and Mineral Show in the United States and the Hong Kong International Jewellery Show attract gemstone dealers, collectors, and enthusiasts from around the globe. At these shows, exhibitors display a wide variety of tanzanite specimens, from raw crystals to finished jewelry pieces, facilitating the exchange and sale of the gemstone on an international scale.
Online Marketplaces
With the growth of the internet, online marketplaces have become a significant avenue for the distribution of tanzanite. Platforms like Blue Nile, James Allen, and Gemvara offer a wide selection of tanzanite jewelry, providing detailed descriptions of the gemstones’ quality characteristics and allowing customers to purchase from the comfort of their own homes. However, it’s important for buyers to be cautious and ensure the credibility of the online sellers.
Conclusion
Tanzanite’s origin in the Merelani Hills of Tanzania is a defining aspect of its identity. The unique geological conditions and formation process in that region give birth to this precious gemstone. From its humble beginnings deep within the Earth’s crust to its journey through mining, cutting, and global distribution, tanzanite has a story that is as captivating as its appearance.
Understanding where it comes from not only enriches our appreciation of its beauty but also helps us recognize the efforts involved in bringing it from the ground to adorn our jewelry pieces. Whether you’re a jewelry enthusiast, a collector, or simply someone who admires the allure of gemstones, knowing the origin of tanzanite adds a layer of depth to your connection with this remarkable stone.
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