- Nail Head - When the pavilion is too deep
Round diamonds with poor proportions, whereby the pavilion is too deep, are called nail head diamonds. This creates a black center in the stone. Gemologists often refer to these stones are “dead” stones
- Natural - Also known as Indented Natural.
A natural is an inclusion that extends into the diamond from the surface. The natural can be a portion of the original surface (or skin) of the diamond (rough) or an opening left when a surface-reaching crystal is worked during polishing.
In order to retain as much weight as possible, diamond cutters sometimes leave an indented natural. This will often collect dust over time and become darker in color. They are however stronger than cavities. Ideally, a natural will not affect the shape or outline of the diamond.
- Needle - A thin, elongated crystal inclusion, which literally looks like a needle.
Diamond clarity refers to how perfect or imperfect the diamond is. Imperfections in the stone are called “inclusions” and there is a wide range of inclusions that exist naturally or that form over time due to wear and tear. These blemishes, especially when eye visible, detract from the value of the stone. Clarity grades range from IF (Internally Flawless) to I3 (eye visible inclusions).
A needle is an inclusion in the stone that is typically either white or transparent. They can occur in isolation or in clusters, which further damages the value of the stone.
- Nick - A small notch on a facet junction
Usually on the girdle or Culet, a nick is a small surface chip on a diamond caused by wear and tear. These typically occur on the stone’s girdle and have a detrimental effect on the price of the stone. Nick’s are classified as inclusions, which are blemished or imperfections. A nick will likely weaken the stone and can be worsened if the diamond is subjected to any further blows.