« How important are outside experts who can understand the uniqueness, specialness and rarity of a gemstone? [ …] If you’re thinking of buying a gemstone, you need an advisor who’s seen a lot of stones. He can relate it to specific points of reference that he has seen with his own eyes. I think that’s hugely important. The ruby is a very good example. A pigeon’s blood ruby is not an exact definition of colour. It’s sort of an agreed upon term that the trade uses to describe a particular, very small spectrum of the red end of the colour scale. So you really need to determine if this is a good pigeon blood. The only way you can determine if something is good or exceptional is by mentally comparing it with many other top-quality stones you’ve seen. A laboratory certificate is not going to do that. » « The same is true for coloured diamonds. In my experience, no blue diamond is like another one. A blue diamond can only refer to other blue diamonds. It’s not like any other gemstone. Don’t think a blue diamond is going to look like a sapphire. It’s an entirely different and special colour and gem. We have to stop thinking of particular types of coloured diamonds, particularly blue, pink, as a category of gemstones — they’re individuals. »