Tanzanite is a beautiful and highly sought-after gemstone that is prized for its unique blue to violet color. But what exactly is tanzanite made of? In this article, we will explore the chemical composition and formation of tanzanite in detail.
Chemical Composition of Tanzanite
Tanzanite is a variety of the mineral zoisite, which is a calcium aluminum silicate. The chemical formula for zoisite is Ca2Al3(SiO4)3(OH), which means that it contains calcium, aluminum, silicon, oxygen, and hydrogen. Tanzanite also contains trace amounts of vanadium, which is responsible for its blue to violet color.
The vanadium in tanzanite is present in the form of a substitutional impurity, which means that it replaces a small percentage of the aluminum atoms in the crystal lattice of the zoisite. This substitutional impurity is what gives tanzanite its unique blue to violet color.
Formation of Tanzanite
Tanzanite is formed in metamorphic rocks, which are rocks that have been altered by heat and pressure. Specifically, tanzanite is formed in a type of metamorphic rock called a schist, which is characterized by its layered structure.
The formation of tanzanite is a complex process that involves a number of geological factors. Tanzanite is formed when the mineral zoisite is subjected to high temperatures and pressures, which cause it to undergo a process called solid-state diffusion. During this process, the calcium in the zoisite is replaced by vanadium, which gives tanzanite its unique blue to violet color.
The formation of tanzanite is also influenced by the presence of other minerals in the rock, such as garnet and diopside. These minerals can affect the temperature and pressure conditions under which tanzanite forms, and can also influence the crystal structure and properties of the gemstone.
Geological Origin of Tanzanite
Tanzanite is found in only one location in the world: the Merelani Hills of northern Tanzania. The gemstone was first discovered in 1967 by a Maasai tribesman named Jumanne Ngoma, who stumbled upon a cluster of blue crystals while tending his cattle.
The Merelani Hills are located in the foothills of Mount Kilimanjaro, and are part of a geological formation known as the Mozambique Orogenic Belt. This belt is a complex geological feature that formed during the collision of the African and Indian tectonic plates, and is characterized by its highly metamorphosed rocks and mineral deposits.
The tanzanite deposits in the Merelani Hills are found in a layer of graphitic gneiss, which is a type of metamorphic rock that contains graphite and other minerals. This layer is located between two layers of marble, which are also metamorphic rocks. The graphitic gneiss layer is thought to have formed from a sedimentary rock that was deposited in a shallow marine environment, and was later subjected to high temperatures and pressures during the formation of the Mozambique Orogenic Belt.
Properties of Tanzanite
Tanzanite has a number of unique properties that make it a popular choice for jewelry. Some of these properties include:
Color: Tanzanite is known for its blue to violet color, which is caused by the presence of vanadium. The color of tanzanite can vary depending on the orientation of the crystal, and can range from a pale blue to a deep violet-blue.
Hardness: Tanzanite has a hardness of 6.5 to 7 on the Mohs scale, which means that it is relatively durable and resistant to scratching. However, it is still softer than many other gemstones, such as sapphire and diamond.
Clarity: Tanzanite is often transparent to translucent, which means that it allows light to pass through it and creates a beautiful sparkle. However, it can also contain inclusions or blemishes that can affect its appearance and value.
Cut: Tanzanite is often cut into a variety of shapes, including round, oval, and pear-shaped, to showcase its unique color and sparkle. The most popular cut for tanzanite is the cushion cut, which is a square or rectangular shape with rounded corners.
Uses of Tanzanite
Tanzanite is a popular choice for jewelry, and is often used in a variety of pieces, including rings, earrings, necklaces, and bracelets. Because of its unique color and sparkle, tanzanite is often used as a centerpiece in jewelry designs.
Tanzanite is also sometimes used in metaphysical and healing practices. It is believed to have a number of properties, including:
Calming: Tanzanite is believed to have a calming effect on the mind and body, and is often used to promote relaxation and reduce stress.
Spiritual: Tanzanite is believed to enhance spiritual awareness and intuition, and is often used in meditation and spiritual practices.
Healing: Tanzanite is believed to have a number of physical healing properties, including promoting healthy skin, strengthening the immune system, and reducing inflammation.
Conclusion
Tanzanite is a beautiful and highly sought-after gemstone that is prized for its unique blue to violet color. It is a variety of the mineral zoisite, and is formed in metamorphic rocks through a process called solid-state diffusion. Tanzanite is found only in the Merelani Hills of Tanzania, and is influenced by a number of geological factors. By understanding the chemical composition, formation, and properties of tanzanite, we can better appreciate and understand this beautiful gemstone.
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