There are rules that govern the way people perceive and process visual cues, which affect how bright or attractive a gemstone’s appearance is, according to GIA’s project manager of cut research Al Gilbertson.
Everyone perceives brightness differently and preferences regarding appearance vary, so understanding what patterns or angle combinations enhance the visual contrast, colour, spread, brightness and scintillation of gemstones is crucial when formulating design strategies and modifying the design of facets. The most appealing and effective design is one that balances brightness, contrast and colour, increases a gemstone’s fire, and has coherent pattern elements even when the gemstone is tilted.
Computer-generated applications with colour-coded contrast maps can be used when faceting coloured gems to improve their brightness and optimise their appearance. Lighting schemes such as ASET (Angular Spectrum Evaluation Tool) and AG (the author’s own environment) can also be used to optimise the appearance of coloured gemstones.
Overall, strong and coherent contrast patterns between the light and dark areas of faceted gemstones can enhance their brightness and colour. Also, gemstones with a high dispersion of light – giving them their characteristic ‘fire’ – make them valuable and desirable as jewellery.