Holloway Cut Adviser (HCA)
Holloway Cut Adviser (HCA) is a free online cut grading system developed in 2000 which was granted a US patent in 2007. The Gemological Institute of America (GIA) developed its cut grading system on the same basis which it began using in 2005.
Holloway Cut Adviser rates a diamond’s cut in lay terms for its spread (how big the diamond is for its weight), light return, fire and scintillation.
Below is an example of an HCA result:
Selected: 62% depth, 57% table, 34.5° crown angle, 40.5° pavilion angle. The result is for a symmetrical diamond with a medium girdle and very good polish HCA scores were adjusted Dec. 15, 2001, and Feb. 6, 2003
|Spread or diameter for weight||Very Good|
|Total Visual Performance||0.6 – Excellent|
within TIC range
HCA does not factor in symmetry, polish or the minor facets. Therefore it is a rejection tool and should be used in conjunction with expert analysis. HCA works very well when combined with an ideal-scope.
A score below 2 (Excellent) means you have eliminated known poor performers (more than 95% of all round diamonds). But a lower score is not the aim; many people prefer diamonds with an HCA score of 1.5 than those below 1.0. The red area on this chart represents the lowest HCA scores and stones near the centre of the red region are often the least affected by small symmetry variations.
A shallower stone, on the lower part of the chart, will look darker when viewed from close up, they are not for everyone. Shallow stones have the advantage of a bigger spread. They are better suited for use as pendants and earring stones where they are not usually viewed from very close proximity (a close observers head obstructs light sources that would otherwise be returned).
Deeper proportioned stones, near the upper part of the red area, have more leakage and reduced light return. Diamonds with a large area of partial leakage table, seen as a pale area with an ideal-scope, are best set in open backed rings so light can get in the bottom or pavilion of the diamond. Garry Holloway FGAA DDT