---
title: "Fused quartz — density, melting point and properties"
description: "Fused quartz has a density of 2,200 kg/m³. Melting point, strength, conductivity, what it is used for, and whether it floats, rusts or is magnetic."
url: https://atoneplace.net/material/fused-quartz/
site: "At One Place"
---

# Fused quartz

**Density of fused quartz: 2,200 kg/m³**

2.20 g/cm³ · 137.3 lb/ft³

Pure silicon dioxide with nothing added, which makes it the extreme case: a thermal expansion coefficient of 0.55 µm/(m·K), about a sixteenth of ordinary glass, so a red-hot tube can be quenched in water without cracking. It also passes deep ultraviolet, which ordinary glass blocks, which is why UV lamps and photolithography optics are fused quartz. It has no melting point and only softens above 1600 °C, so working it needs an oxy-hydrogen flame rather than a normal glassblowing torch.

## Properties

- **Density:** 2,200 kg/m³ — 2.20 g/cm³
- **Tensile strength:** 48–110 MPa
- **Young's modulus:** 72 GPa
- **Thermal conductivity:** 1.38 W/(m·K)
- **Hardness:** 6 Mohs
- **Thermal expansion:** 0.55 µm/(m·K)
- **Floats in water:** No
- **Magnetic:** No

## What it is used for

- Semiconductor furnace tubes and wafer carriers
- UV and infrared optics
- Halogen and arc lamp envelopes
- Optical fibre preforms

## How it compares

*Water is 1,000 kg/m³. Anything with a shorter bar than water floats in it.*

- air: 1.2 kg/m³
- expanded polystyrene foam: 20 kg/m³
- rigid polyurethane foam: 40 kg/m³
- Water — the float line: 1,000 kg/m³
- fused quartz: 2,200 kg/m³
- tungsten: 19,250 kg/m³
- gold: 19,300 kg/m³
- platinum: 21,450 kg/m³

*Water is 1,000 kg/m³. Anything below that floats.*

| Material | Density | Relative to water |
| --- | --- | --- |
| rigid polyurethane foam | 40 kg/m³ | 0.04× |
| expanded polystyrene foam | 20 kg/m³ | 0.02× |
| air | 1.2 kg/m³ | 0.00× |
| fused quartz ← | 2,200 kg/m³ | 2.20× |
| platinum | 21,450 kg/m³ | 21.45× |
| gold | 19,300 kg/m³ | 19.30× |
| tungsten | 19,250 kg/m³ | 19.25× |

## Does it rust?

Fused quartz contains no iron, so it cannot rust. Whether it degrades depends on the material, not on oxidation.

## Is it magnetic?

Fused quartz is not a metal and has no ferromagnetic response.

## Common questions

### What is the density of fused quartz?

2,200 kg/m³, or 2.20 g/cm³.

### Does fused quartz float?

No. At 2,200 kg/m³ it is denser than water.

### Is fused quartz magnetic?

Fused quartz is not a metal and has no ferromagnetic response.

## Related pages

- [Does fused quartz float?](https://atoneplace.net/does-it-float/fused-quartz/)
- [Soda-lime glass](https://atoneplace.net/material/soda-lime-glass/)
- [Tempered glass](https://atoneplace.net/material/tempered-glass/)
- [Borosilicate glass](https://atoneplace.net/material/borosilicate-glass/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)