Instructions
Examine the surface of the gemstone. While real gemstones are likely to have flaws such as scratches and dents, which are natural and result from the gemstone's original environment, imitation gemstones are flawless due to their construction in laboratory settings.
Compare the weight of the gemstone in question to one that is known to be real. Imitation gemstones tend to be heavier than real gemstones because they are more dense.
Hold the gemstone up to the light and take note of how much it sparkles. While it is often difficult to see, imitation gemstones sparkle more than real gemstones due to the fact that the latter have been exposed to different weather conditions.
Check the price tag of the gemstone. Imitation gemstones are much less expensive than real gemstones, as real gemstones are much more rare. If the price seems to be very low for a real gemstone, it is possible you are being sold an imitation.