Diamond Depth: what it is and why it matters
Diamond grading largely relies on the Four Cs to determine stone quality. But, as we saw with Table, there are other factors affecting a diamond quality and fire. Beauty may be in the eye of the beholder, but without stunning flashes of brilliance, your diamond won’t attract much attention … or envy. And that’s regardless of size.
So let’s explore what the diamond depth is and why it matters to your gemstone of choice.
What is diamond depth anyway
In simple terms, diamond depth measures the height of a stone from table to cutlet (the point at the bottom). Depending on your preferred diamond shape, a shallower depth can give the illusion of a much larger stone. However, there is a compromise to make.
Today, the art of cutting diamonds has become quite scientific. For most diamond shapes, something of a formula including number of facets, crown and pavilion angles as well as table to depth ratio. All these measurements are about maximising diamond fire and brilliance.
How the diamond table and depth work together
The diamond table is the largest facet cut in any stone. It’s also the point at which most light enters your gemstone. In ideal cuts, when that light reaches the pavilion facets, it is reflected across the stone and back out the table.
In deeper, narrower cuts light return is less efficient. Much diamond brilliance is lost as light entering through the table reflects across and out of pavilion facets.
In shallow, wider cuts light may not be returned at all. Instead, diamond fire is lost to the pavilion facets, passing from the table and right through the gemstone.
Tolkowsky’s formula is used by most diamond graders to determine stones of maximum fire and brilliance. In this formula, diamond depth should represent 59.3% of the stone diameter. Although, since achieving this precise proportion is a challenge in itself, most high grade diamond sellers recommend a proportion of between 58 and 60%.
How do I know my diamond depth
Information about your diamond depth will be contained in your GIA diamond report or any quality gemstone valuation.