Created gemstones are made in laboratories or factories, not in the earth’s surface. They have virtually the same chemical composition and crystal structure as natural gemstones so their optical and physical properties are very similar. However, they can usually be identified by the difference in their inclusions. Because of the way created gems are made, they may show subtle difference in shape and colour that help to distinguish them from their natural counterparts. Some created gems may also have uneven colour distribution. Created gems have different inclusions from natural gems, so often the best way to tell them apart is to examine them with an eye loupe. It is also possible to enhance authentic gemstones by hiding cracks and flaws, or by heat-treating or irradiating them to improve their colour.