Here's a perfectly pure, Natural Earth Mined Canary Yellow Diamond.

That purity is so important in a vivid yellow.

When a stone has this much color, there are cases of subtones that affect the Vivid Yellow color, and GIA can't always distinguish and or grade these subtle undertones. This one is bright yellow.

The cut is perfect for projecting the Canary color - the stone sings like a canary too.

The nature and placement of the imperfections mean that they are all but impossible to see with a ten power loupe - the diamond is totally eye clean.

The value of a Vivid Yellow is far more dependant on the purity and brightness of the yellow. This stone is worth more than a Fancy Vivid Yellow VVS1 with a less attractive color.

So there you have it.