GIA Clarity Rating... what is the Characteristics section?

[nelmr]

I noticed were the clarity is rated (VS1, SI2, etc) under it says characteristics. I've seen feather, cloud, and other things. What are good characteristics and what are bad ones?

I don't know what the terms found in this section mean. Please, Help!

 

[Blinger]

It all depends on the clarity rating really. These characteristics are also known as inclusions and they are flaws that can be internal or surface-reaching. I would say the worst in order (assuming equal clarity) would be as follows:
twinning wisp, cloud, crystal, cavity, knot, feather, indented natural, needle, natural, pinpoint.

For example, an I1 feather is worse than an SI2 crystal.