1 This high quality hydrothermally lab-grown hexagonal Emerald crystal has the same geometric atomic structure as a natural emerald. One of the easiest ways to tell a natural emerald apart from its lab-grown cousin is that the natural emerald will have many inclusions. Of course there can also be low grade lab-grown emeralds that are much harder to distinguish from naturals. Emeralds, like quartz, grow in superheated water under extreme pressure, which is why they are called hydrothermal crystals.