how is ruby formed or produced?

Question

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Answer 1

a crystalline form of aluminum oxide and one of the most durable minerals that exists; only diamonds are harder. The rich red color arises from the substitution of a small number of aluminum atoms by chromium atoms. Pure corundum is a colorless, trigonal crystal, but it occurs in a wide variety of colors due to infiltrations of other elements. All color variations of corundum, with the exception of ruby, are called sapphires.

Answer 2

Natural rubies are exceptionally rare, but synthetic rubies (sometimes called created ruby) can be manufactured fairly cheaply. Other varieties of gem-quality corundum are called sapphires. It is considered one of the four precious gems together with the sapphire, the emerald and the diamond.

Synthetic rubies have been made since the late 19th century. They have become more common since the work of Auguste Verneuil and the introduction of the flame fusion process. Other processes in which synthetic rubies can be produced are through the Pulling process, flux process, and the hydrothermal process. Most synthetic rubies originate from flame fusion, due to the low costs involved. Synthetic rubies may have no imperfections visible to the naked eye but magnification may reveal curved striae and gas bubbles. The fewer the number and the less obvious the imperfections, the more valuable the ruby is; unless there are no imperfections (i.e., a "perfect" ruby), in which case it will be suspected of being artificial. Dopants are added to some manufactured rubies so they can be identified as synthetic, but most need gemmological testing to determine their origin. Imitation rubies have also been present in the gemstone market for some time. Red spinel, red garnet and even glass have been falsely named as rubies. Trade terms such as balas ruby for red spinel and rubellite for red tourmaline can mislead unsuspecting buyers. Such terms are therefore discouraged from being used by many gemmological associations such as the Gemological Institute of America (GIA).