Although alumina, corundum, ruby and sapphire have different names, shapes, hardness, properties and uses, and are far from noble, their chemical compositions are exactly the same. 1. alumina Pure alumina is a white amorphous powder, commonly known as alumina, with a density of 3.9-4.0g/cm3, a melting point of 2050℃ and a boiling point of 2980℃, which is insoluble in water. It can be extracted from bauxite in industry. Bauxite (Al2O3 3H2O and Al2O3 3H2O) is the main mineral of aluminum in nature. After crushing, it was impregnated with high-temperature sodium hydroxide solution to obtain sodium aluminate solution. Filtering to remove residues, cooling the filtrate, adding aluminum hydroxide crystals, and after stirring for a long time, decomposing the sodium aluminate solution to separate out aluminum hydroxide; After separation and washing, the precipitate was calcined at 950- 1200℃ to obtain α -alumina powder, and the mother liquor could be recycled. This method was invented by Austrian scientist K.J.Bayer in 1888, and it is still the main method for industrial production of alumina, which is called "Bayer method". In the lattice of α-alumina, Al3+ is symmetrically distributed in the octahedral coordination center surrounded by oxygen ions, and the lattice energy is very large, so the melting point and boiling point are very high. α -alumina is insoluble in water and acid, also known as alumina in industry, and is the basic raw material for manufacturing metallic aluminum. It is also used to make various refractory bricks, refractory crucibles, refractory pipes and high temperature resistant experimental instruments; It can also be used as abrasive, flame retardant, filler, etc. High purity α -alumina is also the raw material for producing artificial corundum, artificial ruby and sapphire. It is also used to produce the board base of modern large-scale integrated circuits. Aluminum hydroxide was dehydrated at 140- 150℃ to prepare γ-alumina. It is also called activated alumina and aluminum glue in industry. In its structure, oxygen ions are closely packed in the center of the cube, and Al3+ is irregularly distributed in octahedral and tetrahedral spaces surrounded by oxygen ions. γ -alumina is insoluble in water, but soluble in water. When heated to 1200℃, it is completely converted into α -alumina γ -alumina is a porous substance with an internal surface area of hundreds of square meters/gram, high activity and strong adsorption capacity. Industrial products are usually colorless or pinkish cylindrical particles with good pressure resistance. It is often used as adsorbent, catalyst and catalyst carrier in petroleum refining and petrochemical industry. In industry, it is a deacidifying agent for transformer oil and turbine oil, and also used for chromatographic analysis; It is a neutral and strong desiccant in the laboratory, and its drying capacity is no less than that of phosphorus pentoxide. Heating at 175℃ for 6-8 hours after use can be recycled. At present, the alumina produced by Bayer process accounts for more than 90% of the world's total output, most of which is used to make metallic aluminum, and less than 10% is used for other purposes. Due to different impurities, corundum usually presents different colors. It is blue or yellow-gray, with glass or diamond luster. Its density is 3.9-4. 1g/cm3, and its hardness is 8.8, which is second only to diamond and silicon carbide. It can withstand high temperature. Corundum sand containing iron oxide is called emery, which is dark gray and dark black. It is often used as grinding material to make various sandpapers and grinding wheels. It is also used to process optical instruments and some metal products. Because the output of natural corundum is in short supply, pure α -alumina powder is often sintered in high temperature electric furnace to make artificial corundum, also called fused corundum. It can withstand the high temperature above 1800℃ and is the raw material for manufacturing advanced special refractories. It has the characteristics of high mechanical strength at high temperature, good thermal shock resistance, strong corrosion resistance and low thermal expansion coefficient, and is used to make liner and nozzle of rocket engine combustion chamber. Radar antenna protective cover, nuclear reactor materials, advanced high-frequency insulating ceramics, crucibles for melting pure metals and alloys, high-temperature heating elements, thermocouple protective tubes, various high-temperature furnace linings, etc. Artificial corundum is also used to manufacture bearings and wire drawing dies for precision instruments. China began to produce synthetic corundum from 1958. 3. Ruby and sapphire mixed with a small amount of different oxide impurities are famous rubies and sapphires, which are materials for making precious jewelry, and their particles can be used to make bearings for precision instruments and watches. Ruby is a natural and transparent red corundum. The colors range from light rose to deep carmine, some are purplish, some are starlight, and pigeon blood red has the most commercial value. Red is the reason why the crystal contains a small amount of chromium oxide. Ruby is a gem, the birthstone of July. Ruby English is Ruby, which comes from Latin ruber, with hardness of 9, density of 4g/cm3 and diamond luster. Natural ruby weighs 65,438+0 carats. More than 5 carats are rare, and only one thousandth of the rubies mined every year in the world are of the best quality. Up to now, the largest natural ruby found in the world weighs 3450 carats and is produced in Myanmar. The world-famous superstar ruby weighs 138.7 carats, and the famous pigeon ruby weighs 55 carats. The most famous ruby producing area in the world is the northeast of Mandela, Myanmar. Thailand, Sri Lanka and Cambodia. 1973 in Nganga, Africa, 1978 in Ali spogley, central Australia, and in Hanseatic, Pakistan in the late 1970s, large ruby deposits were discovered one after another. These discoveries are considered to be the three major ruby discoveries in the world in the 1970s. China ruby is mainly produced in Yunnan.
Ruby's English name is Ruby, which comes from Latin and means red. It belongs to corundum group minerals and has a tripartite crystal system. Because it contains chromium, it is red to pink. The higher the content, the brighter the color. Blood-red rubies are most cherished by people, commonly known as "pigeon blood red".
Ruby is hard, only lower than diamond. Its bright red color is called "the crown of rubies". The magnificent and luxurious ruby is the king of gems, the treasure among treasures, and its advantages surpass all gems. Some ancient books think that ruby is "the most precious of the twelve gems created by God when he created everything."
People love ruby and think it is the representative of love, enthusiasm and noble morality, and a symbol of brilliance. Legend has it that people who wear rubies will live a long and healthy life, have a happy love and have a harmonious family. According to legend, in the past, Burmese soldiers would cut a small hole in their bodies and embed a ruby in their mouths. They think that this can achieve the purpose of invulnerability. Ruby is designated as "July Birthday Stone" by the international gem circle, which symbolizes nobility, love and kindness.
The biggest star ruby in the world is Rajanana star ruby. This gem weighs 2457 carats, with six stars and a flat dome. 199 1 year, a ruby and sapphire conjoined with a weight of 67.5 carats was found in Changle county, Shandong province, China. It is called "Yuanyang Gem" and is a rare miracle in the world. In the international gem market, bright red rubies are called "male rubies" and light red rubies are called "female rubies". Mogaoke area in the northeast of Mandalay, Myanmar is the main producing area of high-quality rubies.
Ruby [1] refers to red and pink corundum, which is a kind of corundum. Its main component is alumina (Al2O3), and the red color comes from chromium (Cr). The gem without chromium is naturally sapphire. The main physical properties are: refractive index: 1.762 ~ 1.770, birefringence: 0.008 ~ 0.010; Density: 4.00g/cm3; ; Has a typical absorption line; Hardness is the second largest hardness after sapphire, so only diamonds can carve on its surface, and it is easy to draw a line on the surface of glass with a corner (the hardness of glass is below 6); The cracks are divergent, and there are many common ruby cracks, which are called "ten Hong Jiu cracks" of ruby; It has obvious dichroism, and sometimes the naked eye can see its color change from different angles; Ruby before processing is barrel-shaped and plate-shaped.
Most natural rubies come from Asia (Myanmar, Thailand and Sri Lanka), Africa and Australia, and there are some in Montana and South Carolina. Natural rubies are very rare and precious, but artificial rubies are not difficult, so industrial rubies are all artificial.
Ruby's English name is Ruby, which comes from Latin Ruber, meaning red. The Japanese name of ruby is ルビー. The mineral name of ruby is corundum [2].
The chemical composition of ruby is alumina (Al2O3), which is red to purplish red due to the trace element chromium (Cr3+).
(Note: Pink corundum is not called ruby, but pink sapphire. )
Only red corundum colored with Cr can be called ruby.
Pink corundum is not chrome.
Crystal system: Tripartite crystal system.
Crystallization habit: the crystal shape is often barrel, short column, plate and so on. Aggregates are mostly granular or dense blocks.
Transparency: transparent to translucent,
Gloss: Bright glass luster to sub-diamond luster.
Refractive index: 1.762- 1.770, (+0.009, -0.005)
Birefringence: 0.008~0.0 10.
Deviation: 0.0 18 lower.
Polychromaticity: dichroism is obvious, which is often manifested as purple/brown, crimson/red, red/orange, rose/pink.
Gender: u- (uniaxial negative light).
Special optical effect: starlight effect, which will reflect charming six-shot starlight or twelve-shot starlight under the irradiation of light, and change color.
Mohs hardness is 9,
Relative density: 3.99-4.00
Cleavage: there is no cleavage, and the cleavage at the bottom is developed.
Luminescence: Ruby will emit red and dark red fluorescence under long-wave and short-wave ultraviolet irradiation.
Absorption spectrum: Typical absorption spectrum of chromium. 688nm 690nm absorption double line 668nm 659nm absorption weak line 550nm absorption broadband (yellow-green absorption) blue region 476nm 475nm 468nm purple region absorption.
Ruby is one of the precious varieties in jewelry. Ruby is bright in color, and under the illumination of light source, it can reflect beautiful and moving six-ray starlight, commonly known as six lines, which is caused by the special crystal structure of ruby and its unique optical phenomenon. Ruby is transparent, translucent and opaque, and its colors are water red, pink, pigeon blood red and rose red. Because big gems are very rare, rubies with larger particles are generally fake. There are two kinds of fake rubies: the first is to pass the low-grade rubies off as rubies, and all fake rubies do not have the unique color of rubies. The second is artificial ruby. Artificial ruby is very similar to natural ruby in terms of specific gravity, hardness and color. Intuitively, artificial rubies have uniform texture, no natural impurities, even and positive color, often large particles and lack naturalness.