Lower half length is how far the lower half facets reach from the girdle toward the culet. It is a percentage of that distance.
In more detail
GIA's Excellent range is 70 to 85% and its Very Good range 65 to 90%. By a common rule of thumb, about 75% or less gives fatter hearts in a hearts and arrows viewer. At 80% or more, the hearts are thinner and further apart. The T73's lower halves are at 77%.
On a grading report
On the proportion diagram; GIA reports it to the nearest 5%.
Related terms
- Lower half facet: Lower half facets are the 16 long, thin triangles along the pavilion edge of a round brilliant. There are two between each pair of pavilion mains.
- Star length: Star length is how far the star facets reach from the table edge toward the girdle. It is a percentage of that distance.
- Hearts and arrows: Hearts and arrows is a pattern that a precisely cut round brilliant shows in a reflector viewer. Face-up it shows eight arrows, and face-down eight hearts.
- Pavilion main: Pavilion mains are the 8 long facets of a round brilliant's pavilion that run from the girdle to the culet.