Heshi Bi is a famous jade in Chinese history, known as "the essence of the stars, falling on Jingshan Mountain, transformed into jade, sideways and looking at the color of the blue, the color of the square and the color of the white", which means that if you look at it from different angles, you will see different colors. What mineral is this famous Washi Bi? Unfortunately, the whereabouts of Heshibi are unknown. We can only infer its composition from the descriptions of the ancients. Some scholars believe that Heshi bi should be a white opal.
<h1 class= "pgc-h-arrow-right" > the king of color</h1>
Opal, also known as opal, is a transliteration of the English name Opal. It is loved by the world for its unpredictable colors. A natural scientist in ancient Rome once praised Opal as "a ruby flame, an amethyst blob, an emerald sea." Therefore, some scholars believe that Heshi Bi is not opal, because its color variation is generally limited to light green and white. When the gemstone rotates, the color only changes in depth. Opal, however, is more unique. It can be switched back and forth between various colors, such as light blue, dark blue, dark green, and thick purple. It is a veritable "king of color" in the gem family.
Opal was hailed as the "Queen of the Magic Stone", "Symphony of Colors" and "Visitor to the Magical World". Since ancient times, it has been seen as the embodiment of a rainbow, symbolizing hope and luck, bringing romantic love to people. Today, opal is seen as the birthstone of October, and Opal-loving Australians give it a high status and regard it as the "stone of the nation".
<h1 class="pgc-h-arrow-right" > the color change effect is remarkable</h1>
The color of the gemstone is colorful. Some of them are caused by their own mineral components, called "self-color"; some are mixed with other trace substances in minerals, called "other colors"; some are caused by physical optical processes such as light interference and diffraction, which belong to a "false color". In mineralogy and gemology, the special discoloration phenomenon of opal is called the "discoloration effect" and is a form of false color. In nature, few minerals are arranged in a lattice with small inclusions in a directional manner, causing changes in light. From different directions, their colors will be different. Gemstones with this particular optical property are rare. They are predominantly feldspar gemstones such as moonstone, and opal gemstones such as opal.
How does the color change effect work? Those who have studied physics should remember that there is a typical phenomenon in optics called diffraction. The simple experiment is as follows: place a small hole in the middle of the light source and the observation screen obstacle, when the light travels in a straight line, we can see a bright spot on the observation screen. If the diameter of the hole decreases, a circular halo of alternating light and shade will appear on the observation screen. This is caused by the light waves deviating from the original straight line when encountering obstacles. This instrument that uses the diffraction effect to modulate light is a grating. Opal's mineralogical name is "opal", and its main component is hydrated silica, the chemical formula is SiO2·nH2O, that is, the four valence electrons of the silicon atom form four covalent bonds with the four oxygen atoms. The silicon atom is located at the center of the tetrahedron, and the four oxygen atoms are located at the four apex corners of the tetrahedron. In the structure of the opal, these silica spheres are arranged in an orderly manner in three-dimensional space like tightly packed spheres; these spheres are about 150-300 nm in diameter, and there are many gaps between the spheres, filled with water and air; this structure is like a natural three-dimensional grating. When white light illuminates opal, different wavelengths of monochromatic light diffract continuously diffract with changes in the angle of incidence, so we can see colorful light.
Of course, different opals have different color-changing abilities, which depends mainly on the size of the holes in the opal, and the size of the holes depends on the diameter of the spheres. The larger the diameter of the sphere, the greater the space between them and the more colors they produce. Recall that when we picked up a CD or DVD disc and changed the viewing angle back and forth, would we see rainbow-like colors on the surface of the disc? This is because the surface of the disk is evenly arranged with a series of traces of light, forming a kind of grating, which produces diffraction of light. The discoloration effect of opal is actually the same.
<h1 class="pgc-h-arrow-right" > simple ingredients are not much</h1>
Although the composition of opal is very simple, similar to quartz and glass, not all silica can form valuable opal. In general, opal is formed by the slow precipitation of silica sols produced by the decomposition of silicate minerals, often formed in hot spring sediments, pores or fissure holes in volcanic areas.
The northern foothills of the Tianshan Mountains. Where there is a colorful world, there are many lonely mountains with strange shapes, different colors and bright colors. Some have found fossil wood there: trees hundreds of millions of years ago are buried deep in the ground. Under the action of groundwater, the surrounding chemicals enter the tree, replacing the original wood composition, but still retaining the original wood form, and even the clear wood fiber structure. These fossils are called "silicified wood" because they contain large amounts of silica. What's even more amazing is that some silicified wood also has a discoloration effect, becoming a precious opal.
Not only will plants become opals, but some ancient animals can also be replaced with silica, preserving their internal structure and external features, thus showing a precious discoloration effect. At the International Jewelry Fair one year, an ammonite fossil was very attractive. Ammonite is an extinct marine invertebrate. Ammonite fossils are very precious. In the process of its formation, it gradually takes on the characteristics of opal. No wonder this opal ammonite fossil is so striking.
In fact, opal can be divided into many types: white opal is white opal; black, dark gray and dark blue are black opal; orange and red are fire opal. The main production areas of opal are Australia, Mexico, Brazil, etc., of which the black opal in Australia and the fire opal in Mexico are more famous. In recent years, blue opal has been found in mining in Peru and green opal in Brazil. These are relatively new varieties. China also has opal production. In addition to the northwestern region, in the southern city of Jiangshan in Zhejiang Province, some scholars have found an egg-sized opal in a hole in Jurassic volcanic rock. It was found that opal contained a small amount of galena minerals, making its physical constants such as density, hardness, refractive index and other physical constants higher than that of Australian opal.
In recent years, an alternative opal has emerged in the jewelry market. Its origin is Ethiopia in Africa. Its moisture content is high, up to 20%. It looks crystal clear and is popular. However, if placed in the sun, it will turn dry yellow or even crack within a few days, which is caused by severe water loss inside the opal. Although opal is highly transparent and attractive, it is extremely unstable and difficult to preserve. While soaking in water restores the discoloration effect to some extent, cracks in the gem are still difficult to heal. In general, opal has a water content of less than 10%, but its water content is not fixed. When exposed to air for a long time, almost all gemstones will gradually lose moisture inside, and even gradually appear some small cracks, thus becoming brittle. Therefore, opal needs special maintenance, can not be exposed to the sun, but also as far away from the source of fire as possible.