What exactly the crown angle and what is considered an optimal crown angle for a round diamond?

The crown (which is the top part of the diamond, above the girdle) is very important regarding the diamond's shine, sparkle and fire because it diffuses light into different colors out of the stone.

This angle is calculated in order to provide the best path for the internal light to be viewed and reflected outside of the stone.

An angle that is to steep may diminish a diamond's fire and brilliance, and could indeed cause darkness under the bezel facets, but should not affect the table if that is what you mean.

According to Tolkowsky and his ideal cut, the crown angle should be of 34.5 degrees.

For the AGS the ideal range is between 34 and 35.5 degrees, and for the GIA its 34 degrees.

Still, diamonds with a crown angle between 33 and 36 degrees still have the potential of being very good stones, and reflect light beautifully

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