A diamond girdle can be bruted or polished. Modern diamonds usually have girdles small facets giving them better transparency and stronger brilliance. Step-cut diamonds usually have polished girdles that are not faceted.
Bruted girdles were typically left on old cuts before girdle faceting became common. Counterintuitively the bruted girdles are better at masking the diamond tint, which means that once such stone is repolished and facets are added, the stone might drop a grade or two in color. However, they tend to absorb dirt and oils, requiring periodic cleaning.
- Extremely Thin: May be prone to chipping or breaking unless properly set
- Very Thin: Typically a very good cut grade in diamonds
- Thin, Medium: The most desirable girdle thickness
- Slightly Thick, Thick: Typically an excellent cut grade
- Very Thick: Typically a good to a very good cut grade
- Extremely Thick: Makes a diamond to face-up smaller
Girdle thickness does not affect a diamond’s brilliance and fire.
A diamond with an extremely thin girdle has an elevated risk of chipping along the girdle edge during setting or when worn. However, it does not pose a challenge for a qualified stone setter.
A diamond with an extremely thick girdle increases the diamond weight without visible size increase. Such stone will look marginally smaller from the top than a diamond of similar carat weight with a thinner girdle.
Diamonds with an extremely thick or extremely thin girdle given the choice are less desirable than similar diamonds with moderate girdle thickness.
In the past, girdles were left unpolished after the bruting process, where two diamonds are rotated against each other to give them a round shape. Such girdles with a frosted appearance are called bruted or rough.
“Bearded” girdles have microscopic feathers that look like tiny hairs radiating from the girdle’s edge. This is the result of too much pressure applied during the bruting.