If the stone was made by "nature", the mineral crystal gemstone was measured and carefully designed by "nature" with a ruler. As rare gemstones in minerals, after hundreds of millions of years of baptism of water and fire, they are displayed in the most beautiful posture in front of human beings. The beauty of gemstones lies not only in the beauty of materials, colors, and craftsmanship, but also in the special optical effects of some gemstones, which can be called "beauty in the United States". In general, the optical effects of gemstones mainly include fire color effect, color change effect, cat's eye effect, starlight effect, fluorescence effect and phosphorescent effect. Next, let's enjoy them one by one.
<h1 class="pgc-h-arrow-right" data-track="2" > color change - a brilliant rainbow</h1>
Heshi Bi, the most legendary jade in Chinese history, is known as "the color of the side and the color of the eye, the color of the square and the white". This means that if you look at Hebi from a different angle, you will see different colors. Unfortunately, the whereabouts of Heshibi are later unknown. We can only infer its composition from the descriptions of the ancients. Some scholars believe that Heshi bi should be moonstone, and some scholars believe that it is opal (opal). Moonstone, also known as moonstone, contains calcium, sodium, aluminum, silicon and other elements. When we look at it from different angles, we can see how it changes from white to light blue, like hazy moonlight, so it is called moonstone. The reason for this is that moonstone contains two minerals, calcium feldspar and sodium feldspar. In the lattice of calcium feldspar, the albite molecules are oriented into tiny inclusions, causing light scattering and interference, resulting in changes in the color of the gemstone.
Opal is mainly composed of aqueous silica, also known as "opal". When you look closely at opal, you will find that opal can change back and forth between light blue, dark blue, dark green, dark purple and other colors. Opal is also a true "master of color" in the gem family. Because the silica in the opal is like a tight sphere, arranged neatly in three-dimensional space, forming a natural three-dimensional grating; when the white light is illuminated, with the change of the angle of incidence, the light wave will deviate from the original straight line propagation direction when encountering obstacles, and the monochromatic light of different wavelengths will continue to diffract, so we can see the colored light.
<h1 class="pgc-h-arrow-right" data-track="5" > fires —the brightest light</h1>
When assessing the quality of some gemstones, industry insiders often use the word "fire." If the gemstone is very dazzling, it means "fire is the best." The "fire" here is not a lit flame, nor is it a mineralogical "luster", but a special effect caused by changes in light. For example, diamonds (diamonds) have a strong dispersion ability. That is, when a beam of white light is reflected or transmitted into a faceted gemstone, because different colors of white light have different wavelengths, they will have different refractive indices, so the white light is decomposed and presented a series of chromatograms. This phenomenon is called the dispersion effect. When some well-cut diamonds rotate, this peculiar light flickers as the observer, light source, and the relative position of the gemstone changes. This phenomenon is known as the "gemstone scintillation effect."
When the dispersion effect and the flash effect are displayed at the same time, it becomes a "fire color", that is, a brilliant and strange color light is reflected. The more intense the "fire color", the more colorful and attractive the gemstone becomes. This requires that the material of the gemstone must not only have a sufficiently high dispersion value, but also have the right cut and design. The number of cut faces and the angle between faces must match the optical properties of the gem. Only in this way can the color of the internal fire be fully displayed. For example, diamond has a refractive index of 2.417 and a dispersion value of 0.044. Scientists have found that garnet (a type of garnet) has a stronger dispersion ability than diamonds. Its refractive index is 1.888 and the dispersion value is 0.057. Carefully designed and cut, garnet can exhibit a more intense fire color than a diamond, earning it the "world's brightest gemstone."
<h1 class="pgc-h-arrow-right" data-track="8" > cat's eye - the "genie" in the dark</h1>
Sri Lanka is an island nation in the Indian Ocean and is rich in a special gemstone. Craftsmen cut the top of the gem into an arc. In light, a bright band of light appears in the gem. As the gem rotates, the light band flashes. People call this flash "living light", it is like a cat's eye in the dark, flashing a bright light. In gemology, this particular optical phenomenon is called the cat's eye effect. This gemstone is called opal. The cat's eye in Sri Lanka is actually a golden emerald, a very rare beryllium and alumina mineral. The emerald with its cat's eye effect is a treasure among gemstones. In fact, it's not just opals that have a cat's eye effect. There are also some gemstones such as red beryl, apatite, sapphire, tiger's eye, quartz, tourmaline, and tanzanite that also have a cat's eye effect. For example, an Australian opal is actually black opal.
How does the cat's eye effect occur? During mineral formation, some minerals occasionally carry long inclusions arranged in parallel, or contain fibers arranged in close parallel. If these minerals are cut and polished into a dome-shaped shape, when strong light passes through the minerals, it will reflect and scatter through the light, resulting in a narrow and bright band of light. The experience of gem technicians is that in order to produce the desired cat's eye effect, the gem should be cut and ground into an arc, the bottom of the gem should be parallel to the inclusions and fibers, and the inclusions and fibers should be located in the middle of the gem as much as possible.
<h1 class="pgc-h-arrow-right" data-track="11" > sapphire</h1>
This starlight effect occurs only on hemispherical or oval convex gemstones after cutting and grinding. The most typical are rubies and sapphires. Most of them have six radial starlights, referred to as "six radial stars", and occasionally "twelve radial stars"; some gemstones, such as spinel, garnet, iolite, and kyanite, also have "starlight" that looks very attractive. One might ask: Can the starlight effect be used as a basis for judging the authenticity of a gemstone? From today's point of view, this is not possible. Because natural gemstones with starlight effects are very rare and expensive. In order to make ordinary gemstones produce a starlight effect, jewelers have made great efforts and succeeded. At first, someone found the right place on the surface of the natural gemstone and then carved out several parallel sets of scratches so that the effect of starlight could be artificially created. However, it is clear that the false star effect comes at the expense of destroying the surface of the gem.
Later, as the number of artificial gemstones continued to increase, artificial star gemstones also appeared on the market. In contrast, this effect of natural gem starlight looks like it is emitted from the inside of the gem, and the light is natural; while the starlight of the artificial gemstone is "painted" on the surface of the gemstone, and the light is dim, so the price of the artificial gem is much lower. Starlight – Brilliant Starry Sky Imagine what would happen if the parallel arrangement of the long inclusions in the gemstone or the tight parallel arrangement of the fibers was not just one group, but two or three groups?
In the strong light, you will find those narrow, bright bands of light intersected, like shining stars in the night sky, mysterious and full of charm. The world's most famous sapphire is known as the 'Queensland Black Star'. This sapphire is so famous not only because of its large size, which still weighs 733 carats after cutting, but also because of the 6 crossed bright lines on top of the stone that are polished into an arc under the light. This phenomenon is known as the starlight effect of gemstones.
<h1 class="pgc-h-arrow-right" data-track="16" > phosphorescence - the "truth" of the pearl of the night</h1>
It is said that Suiguo (present-day Suizhou, Hubei) "Suihou" one day encountered a large snake on his way out. The snake was badly injured and struggled on the road. "Waiting" could not bear it, and quickly asked people to bandage the snake and then release it. A few days later, the snake recovered and came to the residence of the "waiting". The serpent said it was the son of the Dragon King. He immediately offered a pearl of the night to repay the kindness of the "waiting" to him. The Eastern Jin Dynasty historian Gan Bao, in his collection of novels "Search for God", made the following description of the night pearl obtained by "waiting": "The diameter is inching, pure white and luminous, and can be candle room." Li Si once wrote: "Your Majesty has the treasure of easy-going, the pearl of the bright moon." This shows that the "waiting" Night Pearl was later acquired by Qin Shi Huang, along with heshi bi. It is said that these treasures may have been hidden in the mausoleum of Qin Shi Huang. The Local Chronicle of the Three Qins records: "In the tomb of the First Emperor, the luminous beads are the sun and the moon, and the temple hangs the sun and moon beads, and the day and night are bright." The so-called "sun and moon beads" here may be "waiting beads".
However, what is a "waiting bead"? Later historians can only speculate based on historical sources. Some people think it's pearls, some say glass, and some say diamonds. At present, the generally accepted claim is fluorite. This is not only because there are fluorite deposits in northern Suizhou, Hubei; more importantly, fluorite is indeed a luminous mineral. There are two kinds of luminescence characteristics of minerals: one is that due to the excitation of external energy, minerals will emit light; but when the external excitation energy stops, the mineral will stop emitting light, which is fluorescence. Second, minerals glow due to excitation of external energy. If the excitation of external energy stops, the phenomenon of mineral luminescence can last for a period of time, called phosphorescence. Some fluorite contain arsenic sulfide, which produces a phosphorescent effect after being exposed or heated by sunlight during the day; arsenic sulfide slowly releases energy at night, producing a faint light that lasts for hours. According to this inference, the ancient night pearl may be this kind of phosphorescent effect of fluorite. In ancient times, it was found that there were always many cobras on a hill. In order to find out why cobras gather here, people observed day and night, and later found that in the dark of night, the rocks here emit a faint light, and many phototropic insects gather here. Because there are many flying insects, frogs will come looking for food. So, the cobra that likes to eat frogs also came. In fact, glowing rocks are fluorite. The origin of the name Chinese fluorite must be the luminous fireflies that people think of.
In short, the various optical effects of gemstones are caused by the reflection, refraction, scattering, interference, diffraction and other phenomena of light caused by their internal structure. Against the backdrop of the gem's different colors, lusters, transparency, and shapes, the optical physics is presented in a fantastic way.
<h1 class="pgc-h-arrow-right" data-track="2" > fluorescence— the cold light that is excited</h1>
Anyone who has used a banknote detector should keep in mind a scenario where when a banknote is irradiated with the detector's ultraviolet light, the real banknote shows a light that is usually invisible to the naked eye. This is made by using the principle that fluorescent substances emit light under ultraviolet light. In 1824, mineralogist Moss noticed that some fluorite exhibited a completely different color under ultraviolet radiation than in sunlight. In 1852, the mathematician and physicist Stokes discovered the presence of fluorescence. Later, geologists discovered some minerals with fluorescent characteristics, such as diamond emitting sky blue or violet fluorescence under ultraviolet or X-ray illumination, fiber zinc ore emitting bright green fluorescence under ultraviolet light, and uranium ore emitting a very faint yellow-green fluorescence under ultraviolet light.
Now, people have clarified the principle of fluorescence production in minerals: when high-energy short-wavelength light is injected into fluorite, the electrons in fluorite will absorb energy and transition from the ground state to the high energy; and the electrons in the high-energy state are extremely unstable, and will jump from the high energy transition energy level to the low energy level, thereby releasing energy and emitting fluorescence. This phenomenon is called the fluorescence effect. Fluorite can fluoresce because it contains some rare earth elements, such as the rare earth elements yttrium and cerium, which can replace a small part of the calcium ions in fluorite. Since these trace elements are not fully integrated into the crystal structure, their electronic structure is in an unstable state and is more likely to be excited, resulting in purple or red fluorescence.