What is the main purpose of bleaching in gemstone treatment?

The main purpose of bleaching in gemstone treatment is to lighten or remove unwanted colors from the stone. This technique is commonly used to improve the overall appearance of gemstones that may have undesirable colorations or inclusions that detract from their aesthetic value. By using bleaching agents, such as hydrogen peroxide, treatments can effectively reduce the intensity of certain colors or blemishes, resulting in a clearer, more desirable appearance.

In contrast, the other options represent different goals that may be associated with gemstone treatments but do not accurately reflect the primary aim of bleaching. Enhancing clarity typically involves processes such as oiling or filling rather than bleaching. Creating a specific color effect is more related to dyeing rather than bleaching, which is focused on color correction. Preventing surface scratches doesn't pertain to bleaching at all, as it addresses a physical concern rather than a color-related issue. Thus, the essence of bleaching lies in its role in color modification for aesthetic improvement.