Cut is the only quality that really gives us humans a chance to shine, no pun intended. All of the other qualities, colour, clarity and carat are determined by nature. Cutting the facets of a diamond requires great skill and many years of training. Cut is arguably the most important quality because a diamond with a higher grade cut will reflect light, creating beautiful ‘fire’ regardless of the colour, carat or clarity of that diamond.
The GIA cut scale labels the highest grade as ‘Excellent’ but you may also see ‘Ideal’ listed for some diamonds. They are comparable. The next grade is ‘Very Good’, then ‘Good’, ‘Fair’ and ‘Poor’. I recommend diamonds with a Very Good cut or above.