The allure of natural gemstones is unparalleled, with their beauty often enhanced through common treatments. Most gemstones in the market today have undergone some form of modification. Many treatments are applied while the gemstone is still in its raw crystal state, making it challenging to determine the exact enhancements made to a particular gem. The chart below outlines the most common treatments for various gemstones used in jewellery. It's important to note that treatments can vary even within a single collection. For instance, in a set of fifty tanzanite rings, while the majority may be heat-treated, some might remain untreated. These enhancements can significantly impact the value of precious stones, with the highest prices commanded by natural gems of exceptional quality that have only been subjected to standard cutting and polishing.