---
title: "Nailhead: meaning in gemology"
description: "Nailhead is a trade term for a poorly cut diamond that looks dark on the table."
url: https://digitalgemology.com/learn/glossary/nailhead
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Light performance

# Nailhead

Also called nailhead diamond

Nailhead is a trade term for a poorly cut diamond that looks dark on the table.

## In more detail

The term names a look, not a measured value. In GIA's cut grading examples, a very steep pavilion and a large total depth give a very dark table. GIA's cut research counts large dark areas in the face-up pattern as a negative trait.

## Related terms

- [Fish-eye](https://digitalgemology.com/learn/glossary/fish-eye): A fish-eye is a dull ring that shows under the table of a round diamond. It is a reflection of the girdle, seen when the pavilion is too shallow.
- [Leakage](https://digitalgemology.com/learn/glossary/leakage): Leakage is light that enters a stone and leaves where the viewer cannot see it, mostly through the pavilion. Lower leakage is better.
- [Windowing](https://digitalgemology.com/learn/glossary/windowing): A window is a face-up area through which you can see straight through a stone. It forms where pavilion facets are too shallow to reflect light, so light passes out of the back.
- [Pavilion depth](https://digitalgemology.com/learn/glossary/pavilion-depth): Pavilion depth is the depth of the pavilion, from the girdle to the culet. It is a percentage of the average diameter.
- [Cut grade](https://digitalgemology.com/learn/glossary/cut-grade): The cut grade rates how well a diamond's proportions and finish work, from Excellent to Poor. GIA gives it only to standard round brilliants in the D-to-Z color range.
- [Contrast (Light Return)](https://digitalgemology.com/learn/glossary/contrast): Contrast is the part of a face-up stone whose light comes from 75° or higher above the girdle plane. This zone lies within 15° of the line of sight, where the viewer's head is.

[All 369 terms](https://digitalgemology.com/learn/glossary)