This paper mainly explains the discovery, color classification, selection and collection investment of Tanzanite. . .
Does the trichromaticity of tanzanite mean that heat treatment is not needed? The answer is not necessarily. .
Hello! Tanzania Oba, introduce yourself first!
Hello, Sankey!
Oba, Tanzania: My name is Tansanti. It is a kind of zoisite, which is produced at the foot of Mount Kilimanjaro in Tanzania, Africa. It is a calcium aluminosilicate mineral with hardness of 6-7, density of 3.35g/cm3, refractive index of 1.690 ~ 1.705, birefringence of 0.009 and obvious trichromaticity. It has been heat treated. Arusha, Tanzania is the only place in the world that produces tanzanite.
Shanky: How did you become famous when you were discovered?
Tanzania Oba: It is said that on a stormy night, lightning ignited the passion of the grassland and ignited a raging fire. After the fire, we were originally mixed with other stones, and the khaki turned blue. Cattle herders passing by Marseille gathered in this lovely blue America. After the news came out, jewelers looking for new varieties came to ask us. 1969, the internationally famous Tiffany company named this kind of gem-tanzanite after the name of the producing country, and it was quickly introduced to the international jewelry market. American women who like to pursue novelty immediately became our fans.
Because of the beautiful and unique "in the center of the sea" in the movie Titanic, everyone knows it. In fact, the gem in the movie is not a blue diamond or sapphire, but a real tanzanite. So, we are famous!
Shanky: Tansang Oba, how many skin colors do you have?
Oba, Tanzania: Our tanzanite is generally blue, purple-blue to blue-purple after "micro-shaping" heat treatment; Others are brown, yellow-green, pink, yellow and green! !
Shanky: Tansang Oba, what is tricolor?
Oba, Tanzania: The above picture shows the colors of tanzanite in different directions. When white light enters biaxial crystal gemstones (such as orthorhombic crystal system, monoclinic crystal system and triclinic crystal system), three beams of light whose main vibration directions are perpendicular to each other form three colors or sometimes two colors with different color densities after differential selective absorption. This phenomenon is called trichromatism of gemstones.
Shanky: Many experts say whether tanzanite is tricolor, that is, whether it has been heat-treated.
Tansanoba: 95% of the blue tanzanite on the market has been heat treated. Heat treatment leads to its beautiful blue and indigo colors. When heated to 600-650℃, the brown color of tanzanite will turn into uniform blue color, mainly because of the price changes of vanadium and V in the composition. Most tanzanite is heated to remove brown, yellow or green multicolor. There is no obvious difference in chemical properties and results between heated and unheated tanzanite. The color of tanzanite will be more stable after heat treatment. Don't worry about this, everyone.
Shanky: Some people are still very concerned about the micro-shaping of gems-heat treatment?
Oba, Tanzania: I personally like this, but fans have the right to know when they buy it, and once again declare that our blue tanzanite is basically micro-shaped.
Shanky: What is the color grading of Tanzanite next year?
Tanzania Oba: There are many standards in the draft, which is quite chaotic! ! We have to sort it out for everyone!
GIA thinks that the best color of tanzanite is bV6/5 or vB6/5. BV and vB represent blue-purple, purple-blue, 6 represents hue, and 5 represents saturation, not black. Other draft standards can be set as 3A, 5A, etc. Only 1% of tanzanite can reach the standard of 6/5 (as shown above).
Shanky: How to choose tanzanite?
Tansang Oba: The color classification is introduced above, and then let's talk about clarity and cutting!
Color: According to the color classification of Grade 5A, it is recommended to choose colors 4A-5A.
Cleanliness: The cleaner the better. There are no scratches and pits on the surface. If there are some obvious flaws, everyone should be tolerant.
Cutting: try not to show the bottom, not too thick, and the ass should be straight and symmetrical. However, some of them can be perfectly inlaid, and the exposed ones are more suitable for pendants and the thicker ones are more suitable for rings.
Chen Shiying Tanzanite Butterfly Works
Shanky: What does OBA think about investing in Tanzanite?
Oba, Tanzania: The value of tanzanite has been rising in recent years, and the price of 20 14 is crazy. The color of 5-year-old tanzanite is relatively rare, and it is difficult for small tanzanite to reach 5-year-old, and it is easy for large tanzanite with 10 carat to reach 5-year-old.
Shanky next year: Can you tell me the reference price of 5A Tanzanite?
Tansanoba: That's enough! Our value will change according to gossip, hype, time and so on! ! In addition, different regions and people have different values about our Tanzanite.