Many natural gems have a synthetic (i.e., lab-grown) counterpart. The man-made material will have essentially the same chemical composition, crystal structure and optical and physical properties as the natural gem gemstone.Many natural gems have a synthetic (i.e., lab-grown) counterpart. The man-made material will have essentially the same chemical composition, crystal structure and optical and physical properties as the natural gem gemstone.Synthetic diamonds are also man-made and have the same properties as natural diamonds. Synthetic diamonds are real diamonds. But the price difference between lab-grown and natural diamonds can be considerable.