> A stone's true properties are physical and measurable: chemical composition, crystal system, hardness, density and the origin of its colour. Knowing them h

*Source : https://meilleures-bijouteries.fr/en/guides/properties-of-stones/*

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● Guide

# Properties of stones: composition, hardness, colours

Published on **26/07/2026** · By **Sébastien Joumel**

In brief

**A stone's true properties are physical and measurable: chemical composition, crystal system, hardness, density and the origin of its colour.** Knowing them helps you choose durable jewellery and spot imitations — far more reliably than "virtues". Here are the essentials, jargon-free.

## Composition: mineral, rock or glass

Not every "stone" is a mineral. [Quartz](https://meilleures-bijouteries.fr/en/guides/amethyst-benefits/) is a mineral (silicon dioxide); [lapis lazuli](https://meilleures-bijouteries.fr/en/guides/lapis-lazuli-benefits/) is a **rock** (several minerals); [obsidian](https://meilleures-bijouteries.fr/en/guides/obsidian-benefits/) is a **volcanic glass**, not crystalline. This nature explains their behaviour (hardness, cleavage, sensitivity).

## Hardness (Mohs scale)

**Hardness** measures scratch resistance, from 1 (talc) to 10 (diamond). It's the key criterion for use: above 6.5-7 the stone takes daily wear; below, it scratches quickly. Find each stone's hardness in our [summary table](https://meilleures-bijouteries.fr/en/guides/crystal-properties-table/).

## Where colour comes from

Colour comes from **trace metals** (iron turns quartz purple or yellow, copper turns malachite green), from **inclusions** (aventurine, tiger's eye) or an **optical effect** (labradorite's flashes, moonstone's veil). Heating or dyeing can alter it — hence the importance of seller transparency.

## Common treatments

Many stones are **treated**: heating (aquamarine, citrine), dyeing (agate, howlite), resin stabilisation (turquoise). These are legitimate _if disclosed_. A too-vivid, uniform colour on a cheap stone should alert you. See our [natural stone jewellery guide](https://meilleures-bijouteries.fr/en/guides/natural-stone-jewellery-guide/).

## And "energy properties"?

To distinguish from physical properties: **the energy or therapeutic properties attributed to stones are traditions and are not scientifically demonstrated** (see sources). They replace no medical advice.

## Sources & references

-   **French National Museum of Natural History** ([mnhn.fr](https://www.mnhn.fr)): composition and mineral families.
-   **GIA** ([gia.edu](https://www.gia.edu)): gemmology and treatments.
-   **Mohs scale**: relative hardness of minerals.

## Frequently asked questions

What are the properties of a stone?

Its measurable physical properties: chemical composition, nature (mineral, rock or glass), crystal system, hardness on the Mohs scale, density and the origin of its colour. These determine a piece's durability and use.

How does a stone's colour form?

From trace metals (iron, copper, chromium), mineral inclusions, or an optical effect (flashes, veil). Heating or dyeing can alter it: a serious seller says so.

Are the energy properties of stones real?

Unlike physical properties, which are measurable, the energy or therapeutic properties attributed to stones are traditions and are not scientifically demonstrated. They replace no medical advice.

## Read also

[

Guide

Amazonite: virtues, calm and communication

](https://meilleures-bijouteries.fr/en/guides/amazonite-benefits/)[

Guide

Amethyst: virtues, meaning and how to wear it

](https://meilleures-bijouteries.fr/en/guides/amethyst-benefits/)[

Guide

Aquamarine: virtues, serenity and meaning

](https://meilleures-bijouteries.fr/en/guides/aquamarine-benefits/)

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