Gemstones that are created artificially in a laboratory to resemble all properties of an original gemstone are called synthetic gemstones. the basic difference between natural gemstones and synthetic ones are that original gemstones may have some impurity in them, but synthetic ones have none. synthetic stones are created under similar conditions that occur in nature, but inside a lab. some synthetic gemstones that are available in the market are moissanite, diamond, emerald, ruby, sapphire, cubic zirconia, and alexandrite. these stones are considered genuine imitations. identify the figure of speech used in the last sentence of the passage.