Natural sapphire also has obvious dichroism, one direction is blue, and the other direction is blue-green. Other gemstones are different in color from natural sapphires and can be distinguished.
In addition, the simplest method can be hardness measurement. Natural sapphires can carve traces on topaz, while other sapphires are difficult to carve traces on topaz. Therefore, when buying jewelry, if there is no instrument around, as long as there is a topaz, sometimes some problems can be solved.
Supplementary explanation of sapphire
Sapphire's English name is sapphire, which comes from the Latin Spphins, meaning blue. The mineral name of sapphire is corundum, which belongs to corundum family. At present, all kinds of gem-grade corundum except ruby are collectively called sapphire.
The chemical composition of sapphire is alumina (Al2O3), which is blue because it contains trace elements of titanium (Ti4+) or iron (Fe2+). It belongs to the tripartite crystal system. Crystal shape is often cylindrical, short column, plate and so on. The geometric shape is mostly granular or dense block. Transparent to translucent, glass luster. Refractive index 1.76- 1.77, birefringence of 0.008, strong dichroism. Not an isotropic body. Sometimes it has a special optical effect-starlight effect. The hardness is 9 and the density is 3.95-4. 1g/cm3. No cleavage, cleavage development. It can produce beautiful starlight under certain conditions, which is called "starlight sapphire".
Sapphire can be divided into blue sapphire and brilliant (non-blue) sapphire. The best color is "cornflower blue" made in India. It is said that sapphire can protect kings and monarchs from harm, and it is called "the stone of kings". Sapphire has been designated as the "September Birthstone" by the international gem circle, symbolizing kindness, loyalty and loyalty. Sapphire is one of the five precious and high-grade gems in the world.
Evaluation and purchase of sapphire. The evaluation and purchase factors of sapphire are color, weight, transparency and purity. Sapphire is characterized by uneven color, undeveloped polycrystalline twins and strong dichroism. Sapphire produced in Myanmar is bright blue (titanium color) because the inclusion can produce six or twelve starlight. Sapphire from Kashmir, India, is a kind of high-quality sapphire, which is cornflower blue and indigo blue with bright color. Sapphires from Sri Lanka, Thailand, China and Australia also have their own characteristics. Sapphire is fragile, so you should avoid bumping and bumping when wearing it.
In nature, there are many kinds of green transparent gemstones similar to emeralds, such as jadeite, tourmaline, fluorite, olivine, garnet, zircon, etc. Among them, tourmaline, fluorite and jadeite are easily confused because of their similar appearance to emeralds. Visually, green jadeite is generally translucent, often in a patchy structure with interwoven fibers, while high-quality emeralds are transparent and crystal clear. Emerald hardness is 7.5-8, while fluorite hardness is very low, only 4. Emerald accounts for a small proportion, while fluorite, tourmaline and jadeite account for a large proportion. Zircon has strong dispersion and obvious ghost.
In addition, there are artificial emeralds and green glass similar to natural emeralds. The biggest difference between them is that most natural emeralds have defects or inclusions, which shows dichroism. Of course, in order to distinguish strictly and correctly, it is best to use identification instruments such as optometry and polarizer.
Identification of cat's eye
In recent years, there is a kind of glass fiber cat's eye ring on the market, which is embedded in gold or silver rings, making people unable to tell the true from the false. The identification method is that when the torus is rotated, several light bands can appear at the arc top of the fake cat's eye at the same time, while there is only one real cat's eye. The fake cat's eye line is rigid, while the real cat's eye line is flexible. True cat's eyes are mostly brownish yellow or light green, while fake cat's eyes are varied in color, such as red, blue and green.
Golden emeralds are second only to diamonds and red sapphires in hardness. Golden emeralds and various changeable stones and opals are not only very beautiful, but also very expensive, because they are extremely rare. Opal is the color-changing effect after Kapson cut emerald with developed vacuum inclusions.
Supplementary explanation of opal
Gold emerald is an alumina containing beryllium, and its chemical molecular formula is BeAl2O4. It belongs to orthorhombic system. Crystal morphology is often short columnar or plate-shaped. Opal has many colors, such as honey yellow, brownish yellow, wine yellow, brownish yellow, yellowish green, yellowish brown, grayish green and so on, among which honey yellow is the most precious. Transparent to translucent. The glass is greasy and shiny. The refractive index is 1.746- 1.755, and the birefringence is 0.008-0.0 10. Dichroism is obvious, the dispersion is 0.0 15, and it is not isotropic. The hardness is 8.5, and the density is 3.71-3.75g/cm3. Shell fracture.
Opal is named after its smooth and rotating color like cat's eye, so it is also called' Opal' in English literal translation. Only emerald cat's eyes can be directly called cat's eyes. Opal has the color of honey, especially a light mark, which will reflect to both sides and become' three light marks', so its price is judged to be very high. In terms of color, cream color and lemon color are not as good as honey color, and brown and gray have lower evaluation. Put the cat's eye in the light. You can display a clear light, and when you turn it, the light bar will shake left and right, which is cat's eye discoloration.
In addition to emeralds, there are other kinds of gems that can show the same luster and deformation effect as cat's eyes. Such as calcium carbide, apatite and blue crystal. There is also a mineral [Tiger Eye Stone] which has the same effect because of its fibrous structure of asbestos, but it can't be compared with the golden green cat's eye. The crown of the king of Iran is inlaid with a yellow-green cat's eye, weighing 147.7 carats.