Corundum is a precious stone, from the point of view of a jeweler. The chemist will say that this is just aluminum oxide, the color of which is impregnated with inclusions of iron, chromium, vanadium, titanium, etc. Impurities, which in percentage terms are about 2%, replace
aluminum in the crystal lattice of the mineral. Surprisingly, the same atoms / ions in different minerals can behave differently. For example, chrome gives corundum a red color, beryl (similar in composition) is green, and chrysoberyl is green in the morning and red in the evening (alexandrite). Such a chameleon.
Corundum transparent intensely colored in the jewelry world has its own names. Red minerals are known as rubies, green as chlorosapphires, blue as sapphires, and colorless as leucosapphires. In ancient times, purple stones were called Bengal amethysts, violet - violet, red-violet - almandine sapphires. Transparent corundum, a stone of orange color, was called padparaj, and yellow-pink - padparadshah.
In ancient times, jewelers and traders used the word “oriental” in the names of various variants of this mineral, which was supposed to emphasize the quality of the stones. Oriental diamonds, oriental emeralds, oriental aquamarines, oriental topazes and oriental chrysolites are all corundums of the corresponding shades. It is good that these names are not used now, otherwise there would be confusion.
Occasionally, corundum stone with the effect of asterism is found. In such specimens, a regular six- or twelve-ray star is visible, the rays of which, when the stone rotates, move along its surface.
Star sapphires and rubies are valued very highly.
Corundum - solid stone (on the Mohs scale - 9). Only diamond is superior in hardness. Due to this property, non-jewelry stones are used as abrasive materials (for cutting and grinding of metal, glass). By the way, the word emery is a synonym for corundum. This mineral is also in demand as a refractory material.
Now the production of artificial corundums has been established. They are obtained by melting bauxite with iron filings (as a reducing agent) in electric furnaces. Most of them are used in technology, only some stones go into jewelry. For example, synthetic rubies are used in the watch industry as supporting stones, leucosapphires in the electronics industry.
Corundums are mined mainly in India, Burma, Madagascar, Thailand, Sri Lanka. In Russia there are also their deposits (in the Krasnoyarsk Territory, Primorye, Chelyabinsk Region, in the Urals).
Corundum is a stone that has long been recognized by lithotherapists. And they use it depending on the color. It is believed that blue stones normalize eye pressure. Reds - improve blood flow, activate the activity of glands, balance metabolism. Violet - relieve various neuralgia and mental disorders. Orange - rejuvenate, improve digestion.
Corundum (stone) as a talisman is excellent for psychologists, doctors, teachers, as well as all women who celebrated their 40th birthday.