The beauty of natural gemstones is unmatched, often enhanced through various common treatments. Most gemstones available today have been modified in some manner. Many treatments occur while the gem is still in its raw crystal form, making it difficult to determine the specific enhancements applied to each gem. The chart below outlines the most common treatments for various gemstones. Sometimes, even within a single design, the treatments can differ. For example, in a collection of fifty tanzanite gemstones, while most may be heat-treated, a few might not be. These enhancements can significantly affect the value of precious stones, with the highest prices commanded by natural gems of fine quality that have only undergone standard cutting and polishing.