In your book, How to Buy a Diamond, you talk about the best proportions for a round diamond. What are the best proportions to look for for a cushion cut diamond?
There are many variations in faceting arrangement for cushion cut diamonds. Also, cutters usually tend to cut cushions to salvage weight–not for maximizing sparkle. Because of these two reasons, I don’t have a guide for proportions of a cushion in my book. It may be most advantageous to you to use the round guideline for cushion brilliant stones. Have a great day!