The main mineral composition of opal is beryllium aluminum oxide. When exposed to strong light or sunlight, opal will reflect a concentrated dazzling light. When the intensity of light source changes, the reflected light band of opal will become stronger and weaker, coarser and thinner, commonly known as' cat's eye '. So how to identify the true and false cat's eye gem? What are the identification methods of opal?
Opal is a kind of precious gem with hardness of 8.5 degrees, second only to diamond, red and sapphire. Its magic power has attracted countless people. High quality opal with more than 10 carats can be worth millions of dollars. Therefore, some unscrupulous businessmen racked their brains to improve some fake and shoddy products, pass inferior products off as good ones, confuse fake products with real ones, cheat consumers, and seek greater interests. So how to identify opal is very important.
Introduction:
Usually, the gems with cat's eye effect are easily mistaken for cat's eye, such as quartz cat's eye, diopside cat's eye, actinolite cat's eye, apatite cat's eye, tourmaline cat's eye, and beryl cat's eye. Due to the parallel arrangement of fibrous structure in these gems, cat's eye phenomenon occurs, but their specific gravity and refractive index are far lower than those of other gems The opal's cat's eye is rough in appearance, the reflected light is not bright and clear, and the color quality is not as pure as emerald. Compared with the real opal, its value is hundreds of times or thousands of times different. Therefore, when we buy opal, we should not trust others' free talk and exaggeration, and we must be cautious. At the same time, we should not forget to buy expensive opal In case of heavy jewelry, the merchant must issue the identification certificate of the jewelry. Of course, it would be better to be accompanied by experts.
The reason for cat's eye is that there are a large number of small, dense and parallel arrangement of filiform rutile inclusions in gem minerals. The incident light is reflected and concentrated into a light to form cat's eye. When a concentrating flashlight is used to irradiate cat's eye gem, at a certain angle, half of the cat's eye appears yellow, while the other half appears milky white. If you use two concentrating flashlights to irradiate the cat's eyes in two directions and rotate the jewels back and forth in the direction of filamentous enclaves, you can see that the cat's Eyeliner will open for a while and then it will be closed for a while.
Identification of opal:
The quality of cat's eye stone is mainly determined by color, eyeliner and weight.
Color: there are many colors of cat's eye, mainly yellow with other hues, the best color is honey yellow, and the others are yellow green, brown green, brown yellow and brown in turn; some silk like inclusions of cat's eye are rutile, and some are empty tubes. Because these tubular inclusions are slender and dense, the cat's eye effect is particularly obvious, even under weak light source. This is incomparable to other gemstones.
Eyeliner: the eyeliner should be straight, uniform, continuous and unbroken, clear and not cloudy, bright and not dull; illuminating from the side of the cat's eye with a single light source, and the colors on both sides of the cat's eye stone are different. When the opal is honey yellow on the left side, it is honey yellow on the left side and milky white on the right side. When the opal is honey yellow on the right side, its color is just the opposite.
Weight: for gemstones, the greater the weight, the greater the value. For cat's eye, it is no exception. There are few gemstones on the market, and those with a diameter greater than 5cm are even rarer.
Artificial opal is made of glass fiber, red, blue and brown yellow, some of which are like natural opal. The differences between the two are: artificial opal has 2-3 bright bands at the top of the arc, while natural opal has only one; the hexagonal honeycomb structure can be seen on both sides of artificial opal by using a magnifying glass; at the same time, the hardness of artificial opal is lower than that of natural opal.