Education

Proportionscope 5.12

Proportionscope (5.12)A proportionscope, first designed and manufactured by GIA in 1967, is an instrument that casts a silhouetted image of the diamond It allows us to check the proportions of...

Measuring Crown Angles 5.11

Measuring Crown Angles (5.11)Diamond cutters use a star gauge to measure the crown angle from the table, which should -- if the stone is accurately cut -- coincide with the...

Crown Angle 5.10

Crown Angle (5.10)The original ideal angle for the crown is 34.5°. Here again, the major gem labs do agree that slight variations from this angle will still produce a well-cut...

Pavilion Angle 5.09

Pavilion Angle (5.09)The original ideal pavilion angle is 40.75˚. The major gem labs do agree that slight variations from this angle will still produce a well-cut diamond. This chosen angle...

The Critical Angle 5.08

The Critical Angle (5.08)The third aspect of light travel in a diamond deals with the internal containment (and distribution). This is the key component in designing the angles of a...

Transmitted Light 5.07

Transmitted Light (5.07)This part is a little more involved -- but not much. Transmitted light is the portion of light that enters the material, or a diamond in this case....