Alexandrite is one of the most amazing stones.
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The main difference between alexandrite and other gemstones lies in its unique ability to change color depending on ambient light. Alexandrite has a bluish-green or grass-green color when white fluorescent artificial lighting is used, but turns violet or ruby-red in sunlight or candlelight. This is called the alexandrite effect phenomenon, and is commonly used with other minerals that are able to change color. For example, garnets, which can change color, are also called garnets with alexandrite effect.
Alexandrite is a variety of the mineral chrysoberyl. The unusual color change effect is due to the presence of chromium ions in the crystal lattice. Currently, natural alexandrite is recognized as one of the most beautiful and rare gems. Of course, this led to the appearance of forgeries in the market, which only remotely resemble the original stone as they fail to reflect the great color changing effect and light play inside natural alexandrite. Corundum forgeries are very widespread.
Czochralski process (pulled)
The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors (e.g. silicon, germanium and gallium arsenide), metals (e.g. palladium, platinum, silver, gold), salts and synthetic gemstones. The process is named after Polish scientist Jan Czochralski, who invented the method in 1915 while investigating the crystallization rates of metals. He made this discovery by accident, while studying the crystallization rate of metals when, instead of dipping his pen into the ink, he did so in molten tin and drew a tin filament, that later proved to be a single crystal.
The most important application may be the growth of large cylindrical ingots, or boules, of single crystal silicon used in the electronics industry to make semiconductor devices like integrated circuits. Other semiconductors, such as gallium arsenide, can also be grown by this method, although lower defect densities in this case can be obtained using variants of the Bridgman-Stockbarger technique.
Synthetic Alexandrite – Czochralski
Chemical formula: BeAl2O4:Cr3+
Crystal system: Rhombic
Hardness (Mohs): 8.5
Refractive index: 1.741-1.75
Inclusions: Inclusions free. (key separation from natural Alexandrite: Fogs, cracks, holes, multi-phase inclusions, quartz, biotite, fluorite)