On the meaning of Top Crystal and Crystal – terms of the “Old Terms”
In the now largely outdated system of "Old Terms", diamonds with a very slight yellow shimmer were referred to as Top Crystal or Crystal. The name is derived from crystal glass. The very faint yellow tone can be recognized even by less experienced people under suitable lighting conditions. Top Crystal was initially defined as "very, very slightly yellowish" and Crystal as "very slightly yellowish", but this terminology has since been replaced by "slightly tinted white" for Top Crystal and "tinted white" for Crystal.
Today it is common to indicate the color values of diamonds in letters. A diamond that was previously classified as Top Crystal is now labeled I, a Crystal diamond with J or K.
