A friend found that a turquoise bracelet he bought last year had gradually "faded" and lost its bright color, and suspected that he had bought a fake.
In fact, real turquoise can also change color.
Why? Let's start with what kind of gemstone turquoise is.
The ancients loved the talisman
In 1900, when archaeologists excavated tombs in Egypt, they found the mummy of a queen in ancient Egypt, wearing 4 gold bracelets on the arm of the mummy, which were inlaid with many opaque blue-green gemstones, although thousands of years later, they were still dazzling. These gems are turquoise. Those 4 bracelets are also considered to be the oldest and most precious turquoise products.
Turquoise, the name comes from the French language, originally meaning turquoise. As early as 5,000 years ago, ancient Egyptians mined this gem on the Sinai Peninsula, which connects Africa and Asia. Most of them were transported into Europe via Turkey, hence the name turquoise (turquoise).
It is said that in order to obtain this gem, the ancient Egyptian pharaohs set up a miner's organization of more than 2,000 people, escorted by the army, after a long journey to the Sinai Peninsula to mine turquoise. These miners work hard every day and only go home once every 3 years. This method of mining continued for 2000 years. Despite this, turquoise production is not high. According to historical statistics, the annual production is only about 400 kilograms.
Turquoise is one of the most valuable gemstones and is revered in many countries. In Western gem culture, turquoise represents the birthstone of December. Westerners believe that wearing turquoise ornaments can be blessed by the gods and bring success and good luck to those who are on expeditions.
In the tombs excavated today, many turquoise ornaments have been found, such as the gold mask of the ancient Egyptian pharaoh Tutankhamun, which used a large amount of turquoise. In 17th-century Russia, turquoise was inlaid in the scabbard of a sword in the hope of asylum. Ancient Persians, ancient Egyptians, ancient Indians, etc. all used turquoise as a talisman to ward off evil spirits.
The use of turquoise on the mainland is even older, as early as the New Age, people have found and used turquoise as an ornament. In the 12th century BC, the people of the Shang Dynasty regarded it as a precious stone, and usually, high-quality turquoise was used to make high-grade jewelry, bracelets, etc., but it could also be used as a craft carving material.
In 1977, Tomb No. 5 of Yin Ruins in Anyang, Henan Province, unearthed more than 1,000 pieces of cicada and frog crafts made of turquoise. In the area of Fufeng and Qishan in Baoji City, Shaanxi Province, there is a Zhouyuan ruins that are 70 kilometers long from east to west and about 20 kilometers wide from north to south, which is the birthplace of Zhou culture and the settlement of Zhou people before the extinction of the Shang. In 2014, mainland archaeologists excavated a carriage here with many parts inlaid with turquoise, which was praised as "the most luxurious carriage of the Western Zhou Dynasty found so far."
The four famous jades are among them
Because of its copper content, the basic color of turquoise is blue-green, and its Chinese name is also due to its "shape like a pine ball, and the color is close to pine green". Turquoise is the product of the interaction between an aqueous copper-bearing solution on the surface of the earth and rocks containing aluminum and phosphorus. In nature, aluminum-containing minerals such as feldspar and phosphorus-containing minerals such as apatite encounter an aqueous solution containing copper, a complex chemical reaction occurs between the two, thereby precipitating in the cracks of the rock and forming turquoise.
The United States is the world's largest producer of turquoise today, and turquoise is produced in Colorado, Arizona, Nevada, new Mexico, etc. The best quality turquoise is from Iran. In addition, Australia, Chile, Peru, Egypt and China also produce small amounts of turquoise.
Among the ethnic groups on the mainland, the most loved turquoise is the Tibetans. The Tibetan people who believe in Buddhism have given turquoise a special meaning, believing that it symbolizes auspiciousness and peace; Tibetans like to wear turquoise, whether it is a necklace, a bracelet, or a hanging ornament on a dress, you can see the figure of turquoise.
The most important source of turquoise on the mainland is not in Tibet, but in the border area of Hubei, Henan and Shaanxi, of which turquoise produced in Hubei is the most famous. Turquoise produced in Hubei is famous since ancient times, known as "Jingzhou stone", and it is known as the four famous jades of the mainland together with the "Hetian jade" in Xinjiang, the "Dushan jade" in Nanyang, Henan and the "Xiuyu" in Xiuyan, Liaoning. Turquoise is also produced in Yueertan, Baihe County, Shaanxi, Liujiaping, Huaichuan County, Henan, Hami, Xinjiang, and Wulan, Qinghai.
The heshi bi in the history of the mainland can be called "the most expensive jade in history", and the Qin state once lured the Zhao state with 15 cities and pools in a vain attempt to occupy it. The story of this heshibi is well known. Because Heshi Bi was produced in Jingshan (in present-day Nanzhang County, Xiangyang City, Hubei Province), also known as "Jingyu" and "Jingbi", some people later believed that Heshi Bi should be turquoise.
There is a Tianyu Natural Museum in Pingyi County, Shandong Province, which houses a rare piece of turquoise from Hubei. Measuring 1.03 metres long, 1.06 metres high and 0.26 metres thick, the gemstone is a treasure of turquoise in its scale, perfect shape and brilliant colour. In April 2009, it was inscribed in the Guinness Book of World Records, becoming today the "largest turquoise in the world's collection".
Heating lost water Gemstone fading
From the perspective of mineral composition, turquoise is a phosphate mineral composed of water and copper and aluminum, which usually contains iron, zinc, etc., and its chemical expression is Cu(Al,Fe)6[PO4]4(OH)8·4H2O. Geologists have found that it is precisely because of the change in the content of copper and iron in turquoise, that is, the content of copper ions, trivalent iron ions and divalent iron ions is different, so that turquoise has a change in color.
Among them, copper ions determine the blue tone of turquoise, the presence of trivalent iron ions makes turquoise red and yellow, and divalent iron ions cause turquoise to produce green hues. This also means that as the content of iron ions in turquoise increases, its color will gradually change from gray-blue to sky blue, and then to blue-green, green, and earth-yellow. In the jewelry world, sky blue turquoise is the most valuable.
From this, it is not difficult to find that at the beginning of the formation of turquoise, the different ratios of copper ions and iron ions have determined that they will have different colors. But thousands of years ago, people could not give a scientific explanation for this. At that time, people had already discovered this strange phenomenon in the color of turquoise: after some people wore it, the color of turquoise changed. They believe that this is a sign that the owner is in danger or physically ill.
Studies have shown that turquoise fades when heated or in direct sunlight. This is because turquoise contains a certain amount of moisture. We can see this from its chemical expression.
In minerals, there is more than one form of water, and there is a kind of water that exists on the surface or inside of the mineral in the form of water molecules through mechanical adsorption, and this water is called adsorbed water; In the form of water molecules, it participates in the composition of the mineral lattice and occupies a certain structural position, this water is called crystalline water; There are also hydroxide ions and other forms involved in the composition of the mineral lattice, this kind of water is called structural water.
In turquoise, all 3 forms of water are present. When the external temperature exceeds 100 ° C, turquoise will lose adsorption water and the color will become lighter; After the temperature continues to rise, its internal crystal structure is destroyed, and the crystalline water and structural water are gradually lost, and turquoise will turn dark brown.
Through the above introduction, it is not difficult to see that after wearing a period of time, the color of turquoise may change; this does not mean that the product purchased by the wearer is a fake, or it may be caused by the high temperature and other adverse effects of turquoise.
In addition, turquoise has less hardness, only 5 to 6, so it needs to be carefully cared for. If you wear turquoise ornaments, try to stay away from fire, sun exposure, prevent bumps, and separate from cosmetics, perfumes and other chemicals to avoid discoloration or damage.