Natural caviar has a characteristic color and size of eggs. If the caviar is of even black color without shades, then this is probably artificial caviar. Another sign of artificial caviar is a white coating on the surface.
To determine the authenticity of caviar, place a few of its grains in a container with hot water. If they have become soft or have dissolved - this is artificial caviar from gelatin and algae. If the water is colored - you bought tinted caviar of other fish. This caviar does not lose color and does not dissolve in water. If you pour boiling water over it, it will practically cook and become dense. Artificial caviar softens and when pressed just burst.
 Pay attention to the density of caviar in the package - when tilting the jar, it should not slide down the walls or lie stuck together.