Cat's eye, "gold emerald with cat's eye effect", "cat's eye", "cat's eye", "cat fine". The opal stone, also known as the oriental cat's eye, is a rare and precious variety in jewelry. The light phenomenon exhibited by the opal is the same as that of the cat's eyes. It is flexible and bright, and can change with the intensity of light, hence the name. This optical effect is called the "cat eye effect." Strictly speaking, "cat's eye" is not the name of a gem, but an optical phenomenon on certain gemstones. That is, when a gemstone that has been ground into a hemispherical shape is illuminated with strong light, a thin and bright reflection will appear on the surface, which is called "cat's eye flash" or "cat's eye light", and then it is named according to what the gem is. If the gem is quartz, it is called "Quartz Cat Eye", if it is a gold emerald, it is called "Golden Green Cat Eye." There are many types of gems that may have a cat's eye flash.
The stone cat eye: also known as the Alexander cat's eye, that is, there is discoloration and cat eyes. It is the rarest and most precious of the gold emeralds. It is produced only in Sri Lanka. The price is quite expensive. It is difficult to see domestic shopping malls within 3 carats.
According to statistics, there may be as many as 30 kinds. In addition to the quartz cat's eye and the golden-green cat's eye, there are mainly "Gemstone Cat's Eye" and "Aquamarine Cat's Eye". Because the golden green cat's eye is the most famous and most precious, it is also referred to as "cat's eye" in the habit. Other cat eyes cannot be called.
Opal belongs to Chrysoberyl in mineralogy and belongs to the gold emerald mineral. Transparent to translucent. Glass to grease luster. The refractive index is 1.746-1.755, and the birefringence is 0.008-0,010. The dichroism is obvious, the dispersion is 0.015, and it is heterogeneous. Hardness 8.5, density 3.71-3.75 g / cm3. Shell-shaped fracture. The difference between opal and other similar gemstone cat eyes and artificial cat eyes.
Gems that produce cat's eye effect in nature include tourmaline, beryl, apatite, quartz, and kyanite, but they are not as precious as gold-green cat eyes. Tourmaline cat's eye: the hardness is small, 7-7.5, density 3.06 g / cm3, refractive index 1.624-1.644. Quartz cat's eye: low hardness, about 6.5, low density, 2.78 g / cm3, low refractive index, 1.44. Artificial cat's eye: Opal made of artificial glass fiber, brownish yellow, blue and red. However, the artificial opal has 2-3 bright bands at the top of the curved shape, and only one bright band appears in the natural opal. Observed by a magnifying glass, the artificial opal has a hexagonal honeycomb structure with a low hardness of about 5, a low density of 2.46 g/cm 3 and a refractive index of 1.44.
Opal identification
The identification of cat's eye gemstones mainly depends on the refractive index, density, hardness, inclusions and other characteristics. Most cat's eye gemstones are gray-brown and translucent, and the opal stones with similar refractive indices are also more. The cat's eye gemstones are all cut into a curved surface. The refractive index itself is only an approximation. If the gemstone is inlaid, its density cannot be directly measured, which makes it difficult to accurately distinguish different cat eye gemstones. Opal is one of the important variants of the gold emerald mineral family. Hardness is 8 or 5 degrees, second only to diamonds and red and sapphire. Its color is mostly yellow, yellow brown, yellow green, green white, coffee and so on. It has obvious golden color, and its Chinese name is also obtained. . A good opal, the bright line of the cat's eye is located in the center of the gemstone face, narrow and clear, and the light is visible. Opal is very precious due to its special light effect, and high-quality opal above 10 carats can be worth millions of dollars. The method for identifying the true and false of the opal is as follows:
1. The main recognition feature of opal is the clear brown-yellow cat's eye. The filamentous inclusions of the opal are rutile, and some are empty tubes. Because these tubular bodies are slender and dense, the cat's eye effect is particularly pronounced, which is also clearly defined under weaker light sources. This is unmatched by other gems.
2, artificial opal is made of glass fiber, there are red, blue and brown, of which the brown-yellow variety is somewhat like natural opal. The difference between the two is that the artificial opal has 2-3 bright bands at the top of the curved shape, and only one natural opal; the sides of the artificial opal are observed with a magnifying glass, and the hexagonal honeycomb structure can be seen; Stone has a lower hardness than natural opal.
3. Illuminate from the side of the opal with a single light source. The colors on both sides of the opal are different. When you look at the yellow opal from the left side, the left side is honey yellow, the right side is milky white, and when it is illuminated from the right side, its color is just the opposite.
In recent years, as the number of people traveling to Taiwan in mainland China has increased significantly, the jewellery and jade consumption disputes have also increased. A considerable part of the dispute is due to the different standard names or commercial names of jewels and jade on both sides of the strait, which has caused consumer conflicts. The most complaints are the opal, which refers to the “Golden Green Cat Eye†on the mainland, that is, the gold emerald, while the opal sold by Taiwan is the nephrite cat's eye. Although the golden green cat's eye and the nephrite cat's eye are also called cat's eyes, the value of the two is very different. For example, before a citizen of Fuzhou went to Taiwan to spend 2,500 yuan to buy a "cat's eye ring", after the inspection of the inspection team of the Fujian Province Jade and Stone Association, the opal is actually nephrite, not the gold emerald cat's eye, the ring The actual value is only about 200 yuan.
According to industry insiders, after the mutual recognition of cat jewellery naming standards between Fujian and Taiwan, opal is specifically referred to as “golden green cat's eye†or gold emerald, while opal sold in Taiwan refers to “soft jade cat's eyeâ€. Consumers can also avoid some disputes when they buy.
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