- Table – the large facet at the top of the diamond.
- Table Percentage
For a round brilliant cut, the average width of the table as a percentage of the average diameter of the diamond. For fancy shapes, it is the width of the table as a percentage of the width of the entire diamond.
- Treated Diamond – a diamond that has been altered to affect color or clarity.
There are a number of treatments that a diamond can undergo to improve either their color or clarity grade. While these improve the visual appeal of the stone, this has a negative effect on the value. The reason being is that a diamond that has been artificially improved is not as rare as a diamond that is naturally of a high color or clarity grade.
To improve the color of a stone, HPHT (High Pressure High Temperature) is a common treatment. This involves exposing the stone to incredibly high pressure and temperatures to change the color of the diamond.
To improve the clarity of a stone, laser drilling and fracture filling is a popular choice. By drilling a small hole into the stone, burning away the blemish and inserting a liquid like gel, the clarity of a diamond can be vastly improved.
Any paperwork you have should detail treatments. It is worth noting that the GIA will not issue a certificate for diamonds that have undergone what is considered to be a non permanent treatment. The reason for this is that once the treatment wears off, the certificate will no longer be accurate. A jeweler should always disclose any treatments a stone has undergone, whether they are permanent or not, when selling a diamond.
- Trillion Cut – See Shape.
- Twinning Wisp – a series of pinpoints and/or clouds that form in the diamond’s growth plane.
This is a clarity characteristics that negatively impacts the diamond’s value.