Color and internal content on the sapphire like natural stones such as tanzanite and blue spinel. Visually tell them apart is almost impossible. For this purpose there is a special device that measures the refraction of light. It is called Refractometer. With its help determine the authenticity of some precious stones. If you measure the refraction of light sapphire, then the index will be equal to 1, 76, tanzanite and 1.7, blue spinel – 1, 72. After the measurement, be sure to look at the stone in profile. If the stone has the same color top and bottom, it's real.
Sapphire is second in hardness stone after the diamond, so like him jewelry doesn't go with it in comparison. Like the sapphire, and many stones have the deep blue color. But, for example, the spinel is too dark to be with him, to confuse, tanzanite slightly reddish hue, and the aquamarine color resembles an ocean wave.
Natural stone should have a visually distinct natural particles (inclusions). Scammers in large volumes create fake synthetic sapphire, which are much cheaper. In such rocks instead of inclusions of natural character under a magnifying glass you can see the gas bubbles. In these sapphires don't. Forgery can also be particles of flux or copper. And yet, do not rely entirely on their own vigilance. To distinguish natural sapphire from a fake can only specialist.
Sapphire is one of those gems that possess high purity. But the complete lack of inclusions suggests that you are trying to sell synthetic fake. Choosing the decoration with a sapphire, please note, recorded it somewhere in the level IF (purity) of the stone. The fact that he is not defined for sapphires, but if the seller tells you the specific data that it sells natural stone.