Mankind has learned to forge precious stones since ancient times. But if before the extraction of precious stones was not carried out on an industrial scale, today, with the development of technology and the discovery of new deposits, the market is so saturated with real gems that it is no longer so profitable to counterfeit or grow them in artificial conditions. Although fraudsters have always been at the forefront of technological progress - therefore, the conveyor of counterfeits works without stopping.
Please note: sapphire (according to international classification) can have not only traditional blue, but also yellow, blue, pink and even black. Sapphire is corundum, which is an aluminum oxide. Red corundums are rubies.
Do not forget that there are so-called natural "doubles" of sapphire, which are an order of magnitude less than "pure" stone - cordierite ("water sapphire", with an admixture of magnesium), tourmaline, cyanite (disten) and many others. It is possible to single out a real sapphire among such a variety only by its physical and chemical properties, by contacting a specialist.
Take special care if the color and clarity of the stone is absolutely even, despite the fact that today almost all stones are "pre-sale". However, any real stones always contain natural inclusions, while plastic or glass fakes do not. Artificially grown stones often contain gas bubbles, color zoning, and minute gold or platinum inclusions. Therefore, look at the stone at the light or take a magnifying glass for this.
Place the stone to be tested in a high density gemological colorless liquid. If the sapphire is real, then it will sink to the bottom of the container, but if it is a fake, the stone will remain on the surface.
If you have items with other gemstones, such as emeralds or rubies, try carefully scratching the gem you are testing with them. Since sapphire is a hard stone (only a diamond is harder than it), there should be no traces left on it.
Hold the stone in your hands. If it heats up quickly, then it is synthetic, but if it remains cold for a long time, this is a real sapphire.
If you still have doubts about the purity of the stone, invite an expert to conduct additional research.
Buy stones and jewelry only from reputable jewelers or salons that have been working in this market for more than a dozen years. Fraudsters also carry out "pre-sale preparation" of stones. For example, inexpensive bluish-gray natural sapphires, after heating, acquire a deep, saturated blue color for some time.