---
title: "Quartz: meaning in gemology"
description: "Quartz is the mineral species of amethyst and citrine. It is silicon dioxide in a trigonal crystal."
url: https://digitalgemology.com/learn/glossary/quartz
image: https://digitalgemology.com/img/og-digital-gemology.png?v=d224fb01
---

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[Glossary](https://digitalgemology.com/learn/glossary) · Colored gemstones

# Quartz

Also called silicon dioxide

Quartz is the mineral species of amethyst and citrine. It is silicon dioxide in a trigonal crystal.

## In more detail

Quartz has a refractive index of 1.544 to 1.553, a specific gravity of 2.65 and a hardness of 7. Its low refractive index needs a steep pavilion. Quartz turns the plane of polarized light, so its conoscope figure is a bull's-eye. Laboratories grow quartz only by the hydrothermal method.

## On a grading report

Labs print 'quartz' as the identification and the variety, such as amethyst or citrine.

## Related terms

- [Amethyst](https://digitalgemology.com/learn/glossary/amethyst): Amethyst is the purple variety of quartz. Iron in the crystal, together with natural radiation, causes its color.
- [Citrine](https://digitalgemology.com/learn/glossary/citrine): Citrine is the pale yellow to brownish orange variety of quartz.
- [Ametrine](https://digitalgemology.com/learn/glossary/ametrine): Ametrine is quartz that is part amethyst and part citrine: purple and yellow zones in one crystal.
- [Hydrothermal growth](https://digitalgemology.com/learn/glossary/hydrothermal-growth): Hydrothermal growth makes synthetic crystals in a hot water solution under high pressure.
- [Gem species](https://digitalgemology.com/learn/glossary/gem-species): A gem species is a mineral with one chemical composition and one crystal structure, such as corundum, beryl or quartz.

## Learn more

- [Amethyst 3D models and cutting files](https://digitalgemology.com/gemstones/amethyst)
- [Polariscope](https://digitalgemology.com/about/how-we-measure/polariscope)
- [Refractometer](https://digitalgemology.com/about/how-we-measure/refractometer)

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