What is the Difference Between Fused Silica and Quartz

The key difference between fused silica and quartz is that fused silica contains non-crystalline silica glass whereas quartz contains crystalline silica.

Fused silica is also known as fused quartz. It is a glass containing almost pure silica in an amorphous form. Quartz, on the other hand, is a mineral compound containing silicon and oxygen atoms.

CONTENTS

1. Overview and Key Difference
2. What is Fused Silica 
3. What is Quartz
4. Fused Silica vs Quartz in Tabular Form
5. Summary – Fused Silica vs Quartz

What is Fused Silica?

Fused silica, also known as fused quartz, is glass containing almost pure silica in the amorphous form. This type of glass is different from other available glasses on a commercial scale because the ingredients of the fused quartz production are different from others. These ingredients cause a change in the optical and physical properties of glass, including the lowering of melt temperature. Therefore, fused silica has a high working temperature, high melting temperature, etc. This also makes the glass less desirable for some common applications.

We can produce fused silica by fusing/melting high purity silica sand containing quartz crystals. The four common types of fused quartz in industries include type I, II, III, and IV.

Type I – produced by induction melting of natural quartz in the vacuum of inter atmospheres

Type II – produced by fusion of quartz crystal powder at a high flame temperature

Type III – produced by burning silicone tetrachloride in a hydrogen-oxygen flame

Type IV – produced by burning silicone tetrachloride in a water-vapour free plasma flame

What is Quartz?

Quartz is a mineral compound containing silicon and oxygen atoms. It contains silicon dioxide (SiO2) molecules. Moreover, it is the most abundant mineral on Earth’s crust. Though it contains SiO2, the repeating unit of this mineral is SiO4. This is because the chemical structure of quartz contains one silicon atom bonded to four oxygen atoms surrounding it. Hence, the geometry around on silicon atom is tetrahedral. However, one oxygen atom is shared between two tetrahedral structures. Therefore, the crystal system of the mineral is hexagonal.

Furthermore, quartz crystals are chiral. That means quartz exists in two forms as the normal α-quartz and the high-temperature β-quartz. The alpha form can transform into the beta form at around 573 °C. Looking at their appearances, some quartz types are colourless and transparent, while other forms are colourful and translucent. The most common colours of this mineral are white, grey, purple, and yellow.

What is the Difference Between Fused Silica and Quartz?

Fused silica or fused quartz is a glass containing almost pure silica in an amorphous form. Quartz is a mineral compound containing silicon and oxygen atoms. The key difference between fused silica and quartz is that fused silica contains non-crystalline silica glass whereas quartz contains crystalline silica. Moreover, fused silica is made by fusing/melting high purity silica sand containing quartz crystals, while quartz naturally occurs and it is industrially prepared by using “seed crystal” ( a small piece of carefully selected quartz) on which the quartz grow.

The below infographic lists the differences between fused silica and quartz in tabular form for side by side comparison.

Summary – Fused Silica vs Quartz

Fused silica is also named as fused quartz, and it is a glass containing almost pure silica in the amorphous form. Quartz is a mineral compound containing silicon and oxygen atoms. The key difference between fused silica and quartz is that fused silica contains non-crystalline silica glass, whereas quartz contains crystalline silica.

Reference:

1. “Fused Silica.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “EPROM Intel C1702A” By Author : Poil 01:10, 17 Apr 2005 (UTC) – Author personnal collection. (CC BY-SA 3.0) via Commons Wikimedia
2. “Quartz, Tibet” By JJ Harrison – Own work (CC BY-SA 2.5) via Commons Wikimedia