Which type of cut usually leads to a gemstone having less brilliance?

A shallow cut in gemstones typically results in less brilliance due to the geometry of light reflection and refraction within the stone. When a gemstone is cut too shallowly, light enters the stone and often escapes out of the bottom or sides rather than being properly refracted within the stone and bouncing back to the observer's eye. This lack of internal reflection diminishes the sparkle and overall brilliance that is characteristic of well-cut stones.

In contrast, deeper cuts can often enhance brilliance by allowing light to bounce around inside the gem before exiting, but if a cut is too deep, it can lead to other issues such as a loss of weight or poor visual performance. Step cuts, with their flat facets, focus more on clarity and color rather than brilliance, while mixed cuts combine elements of both brilliant and step cuts to maximize both appearance and light performance. However, the shallow cut specifically is known for its direct impact on reducing overall brilliance due to the way light interacts with the gemstone.