Articles about Diamond Grading

On many websites you will see it said that the pavilion main facets drive light return. Top labs and many grading systems use the pavilion angle as a basis for assigning a cut grade.

Is this correct?

A pre-purchase, screening tool for the consumer. An explanation tool for the appraiser.
Intended to gauge the credibility of represented color, clarity and cut grades compared to GIA or AGSL grading.
Highest Confidence: SCORE = 1
The grade will exactly match GIA/AGS 65% to 70% of the time. This is about the level at which these lab’s own graders match each other’s grades while working on diamonds. This grade ONLY applies to loose diamonds. Only very highly experienced, properly trained and equipped graders can claim this level of confidence. Very few gem laboratories or gemologists actually have this degree of competence.

Many of us know Al Gilbertson as an esteemed cutter, gemologist and innovator. Add "mythbuster" to his titles. Mr. Gilbertson has produced a gem of a book, sure to be a page-turner for enthusiasts of "ideal" diamond cutting origins.

The problem started back in 1812 when Friedrich Mos developed the Mohs scale for gemstone hardness. He took a selection of stones and used them to scratch each other. Harder stones would scratch softer ones and he organized them into a ranking from 1 – 10 with diamond being the hardest. Nothing will scratch a diamond except another diamond. This is correct and diamond is in fact quite a bit harder than 2nd place (sapphire) and it has lead to a long standing belief that diamonds are indestructible.

Why a Two-Dimensional Cut Grading System is Pass?