---
title: "Coating: meaning in gemology"
description: "Coating is a thin film, paint or ink on the surface of a gem that changes its color or look."
url: https://digitalgemology.com/learn/glossary/coating
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Treatments and origin

# Coating

Also called coated diamond, surface coating

Coating is a thin film, paint or ink on the surface of a gem that changes its color or look.

## In more detail

On a diamond, a very thin layer can mask the body color. Coatings can scratch and wear off, and once a gemologist suspects one, it is easy to identify. GIA treats coating as unstable and issues no grading report for a coated diamond. A coated stone cannot be called padparadscha.

## On a grading report

Labs state the coating. For a coated diamond, GIA issues an Identification Report instead of a grading report.

## Related terms

- [Color treatment](https://digitalgemology.com/learn/glossary/color-treatment): A color treatment is any process that changes a diamond's color, such as HPHT processing or coating.
- [Fracture filling](https://digitalgemology.com/learn/glossary/fracture-filling): Fracture filling is a clarity treatment that injects a glass-like filler into a crack to make it less visible.
- [Identification Report](https://digitalgemology.com/learn/glossary/identification-report): An Identification Report states what a material is, without color or clarity grades. GIA issues one for simulants and for diamonds with unstable treatments, such as coating or fracture filling.
- [Treatment](https://digitalgemology.com/learn/glossary/treatment): A treatment is any process, other than cutting and polishing, that changes a gem's color or apparent clarity. Anyone who sells a treated gem must disclose the treatment.
- [Disclosure](https://digitalgemology.com/learn/glossary/disclosure): Disclosure is telling the buyer, before the sale, that a gem is treated, laboratory-grown or an imitation.
- [Padparadscha](https://digitalgemology.com/learn/glossary/padparadscha): Padparadscha is a sapphire of soft pinkish orange to orangey pink. Its tones are pastel and its saturation low to medium.

## Learn more

- [Comments, treatments and lab-grown origin on a diamond report](https://digitalgemology.com/learn/grading-reports/diamond-report-comments-treatments-origin)

[All 328 terms](https://digitalgemology.com/learn/glossary)