Properties of Fused Quartz

Quartz silica is found almost everywhere in nature, and represents almost 1/3 the mass of the earths crust. Vitreous Silica is the generic term used to describe all types of silica glass, and manufacturers refer to the material as either Fused Quartz or Fused Silica.

Fused Quartz is manufactured by melting naturally occuring crystalline silica, such as sand or rock crystal. The production method is either electrically fused or flame fused. Afterward, items will appear transparent, translucent, or opaque; making it possible to create a wide range of products.

Fused silica, commonly referred to as synthetic fused quartz, is produced using high purity silica sand that is manufactured from SiCL4. The finished product’s appearance will be transparent.

Vitreous Silica, in all its forms, offers a variety of properties such as:

  • Permeability
  • Extreme Hardness
  • Very Low Coefficient of Thermal Expansion
  • Resistance to High Temperature
  • High Chemical Purity
  • High Corrosion Resistance
  • Extensive Optical Transmission from Ultra-Violet to Infra-Red
  • Excellent Electrical Insulation Qualities
  • Remarkable Stability Under Atomic Bombardment



Density2.2 x 103 kg/m3
Hardness5.5–6.5 Mohs’ Scale
570 KHN100
Design Tensile Strength4.8 x 107 Pa (N/m2) (7,000 psi)
Design Compressive Strength>1.1 x 109 Pa (160,000 psi)
Bulk Modulus3.7 x 1010 Pa (5.3 x 106 psi)
Rigidity Modulus3.1 x 1010 Pa (4.5 x 106psi)
Young’s Modulus7.2 x 1010 Pa (10.5 x 106 psi)
Poisson’s Ratio0.17
Coefficient of Thermal Expansion (20°C–320°C)5.5 x 10-7 cm/cm °C
Thermal Conductivity (20°C)1.4 W/m °C
Specific Heat (20°)670 J/kg °C
Softening Point1683°C
Annealing Point1215°C
Strain Point1120°C
Electrical Resistivity (350°C)7 x 107 ohm cm
Dielectric Properties (20°C, 1 MHz)
          Strength5 x 107 V/m
          Loss Factor<4 x 10-4
          Dissipation Factor<1 x 10-4
Index of Refraction1.4585
Constringence (Nu value)67.56
Velocity of Sound-Shear Wave3.75 x 103 m/s
Velocity of Sound/Compressional Wave5.90 x 103 m/s
Sonic Attentuation<11dB/m MHz
Permeability Constants (700°C)(cm3 mm/cm2 sec cm Hg)
          Helium210 x 10-10
          Hydrogen21 x 10-10
          Deutrium17 x 10-10
          Neon9.5 x 10-10
To view an enlarged version of this chart, click HERE