Gems, artificial

Once the structure of a natural gem is known, it is usually not very difficult to make the gem artificially. For example, rubies and sapphires are made on a large scale by fusing Al(OH)3 with the appropriate transition metal salts at approximately 1200°C to make the doped corundum. With these techniques... 

Because chemical and structural properties of natural and artificial gems are very similar in this case, the possibilities of Raman and LIBS methods are rather limited. It was found that another laser-based techniques could be very effective for rapid spectroscopic discrimination between natural and synthetic emeralds, rubies, and alexandrite (Armstrong et al. 2000a,b). The first one is DRIFTS (Diffuse Reflectance Fourier Transformed Infra-Red Spectroscopy)... 

Luminescence intensity with very rare exceptions is much higher in artificial gemstones compared to natural counterparts. It may be explained by the fact that the activator contents are usually higher in laboratory made gems, while the quenching center concentrations are lower. 

Fine and super-fine structure of luminescence lines of Cr and TR are narrower in artificial gems. The reason is that in natural precious stones many optically active centers are usually present, while in artificial ones only one or two occur. 

Aluminum Fluosilicate or Aluminum Silico-fluoride, Al2(SiF6)3 mw 480.83 wh pdr si sol in cold w sol in hot w. Can be prepd by treating alumina crihydrate with fluosilicic acid. Used for prepn of artificial gems, enamels glass... 

Berthelot notes that the artisan who used these notes while a practical worker in metals, especially the metals used by the jewelers, seemed to be a stranger to the arts of enamels and of artificial gems. It is, therefore, of great interest to discover that the Stockholm papyrus supple-... 

ALEXANDRITE. A variety of chrysoberyl, originally found in the schists of the Ural Mountains. It absorbs yellow and blue light rays to such an extent dial it appears emerald green by daylight but columbine-red by artificial light. It is used as a gem, and was named in honor of Czar Alexander II of Russia See also Chrysoberyl. 

Spinel is a colorless magnesium aluminate (MgAl204) of cubic structure. It is hard and durable, but, like white sapphire, it is not a good diamond substitute because it has a low refractive index and lacks brilliance. However, it is readily doped to produce other gems of various colors. Artificial ruby, for example, is often natural red spinel, and most synthetic blue sapphires on the market are actually blue spinel. 

Precious stone the most prized gem species usually limited to only four ruby, sapphire, diamond and emerald all others are semi-precious this is an artificial term used only in marketing and has nothing to do with quality, size, or value. 

One method involves the microwave-induced removal of hydrogen from methane (CH, swamp gas) in a very sparse gas phase so that carbon atoms, stripped of most of their hydrogen, can settle out on the substrate and start building diamond crystals. In the past, the diamonds formed in this process were tiny and only suitable for industrial applications, but lately gem-quality crystals have been grown. The artificial diamond is virtually indistinguishable from the natural diamond because they are both just a crystalline form of carbon. 

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