Cut
An easy way to identify an old mine diamond is by the look of its table. There will be a visible circle at the center of the table as a result of the cut’s large culet. The culet is located at the very bottom of a diamond’s pavilion and a diamond doesn’t always have one. When it does, the culet will affect the stone’s light performance letting light escape through the bottom of the stone instead of returning it through the top. The presence of a culet will create a dark-ish circle.
Cut quality is going to vary greatly for old mine cut diamonds. Because they are cut to sparkle under candlelight or dim lighting conditions, most antique diamond cuts had high crowns, deep pavilions and broad facets. Then since they were cut and polished by hand with artisans using only basic tools, old mine diamond cuts developed to lack uniformity and feature significant variations in symmetry.
It’s important to understand that grading organizations like GIA will assign some of the lowest ratings for polish and symmetry to old mine cut diamonds because it’s a modern system being applied to an antique process. A certain level of the appeal for old mine diamonds rests in their unrefined beauty.
Color
Many antique diamonds have what is usually described as a warm color. Again, this was done on purpose to accentuate the characteristics of a diamond under dim lighting like candlelight. When shopping for old mine cut diamonds, you’ll likely notice that many of the available stones have colors in the K range and below.
A main reason why the color grade is so low is that many of the colorless antique old mine diamonds – in the D-H range – have been recut into modern brilliant diamonds over the years. It’s widely accepted that the warm color of an old mine diamond is part of its appeal and a diamond of this age shouldn’t be judged by modern standards.
Clarity
An eye-clean diamond is always the standard when it comes to clarity, and that’s no different for old mine cut diamonds. The clarity grade of an old mine cut is going to be accurately described by the certification agency’s rating just as would be the case for modern brilliant diamonds.
The important thing to remember about old mine diamonds when it comes to clarity is the open table at the center of the stone when facing up. This area allows for a direct line of sight to the bottom of the ring and culet. So if any inclusions or blemishes are located in this area, they will be much more apparent.
Carat
Most old mine cut diamonds were cut, polished and worn a very long time before diamond engagement rings became a mainstay piece of jewelry. As such, they are often larger than the 1 carat range diamonds used in most modern engagement rings today.
Another feature of their antique history is that old mine cut diamonds were cut with a similar goal in mind as modern day princess cut diamonds – to limit rough wastage and retain carat weight. However, because they are hand-cut and polished, the way that the weight is distributed throughout the diamond will vary, so it’s always important to see an old mine diamond in person or at the very least, from many different angles.
