Posted By:
E, DanielI don't think you can determine what is rare, without reference to RARITY. Something cannot be simply beautiful or deeply appreciated - and thus rare, its beauty must be so uncommon as to establishing rarity of such presentation.
Rare to me requires using the word in a sentence......as in, this animal is rarely encountered (aka white rhinos). The idea being, that specimens of rarity are more known by the story telling than in first hand experience, and that very few can personally be attained in-hand. I would think a number less than 10 equals rare.
4 Carat Internally Flawless Fancy Yellow diamonds are rare. They exist, but you are unlikely to ever see or come across one (unless Leon turns to collecting diamonds and posts a scan for us 
).
Daniel