technical properties category



Silica is found almost everywhere in nature, and represents almost 1/3 the mass of the earth’s 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 is a transparent glass with an ultra-high purity and improved optical transmission.

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



Density 2.2 x 103 kg/m3
Hardness 5.5–6.5 Mohs’ Scale
  570 KHN100
Design Tensile Strength 4.8 x 107 Pa (N/m2) (7,000 psi)
Design Compressive Strength >1.1 x 109 Pa (160,000 psi)
Bulk Modulus 3.7 x 1010 Pa (5.3 x 106 psi)
Rigidity Modulus 3.1 x 1010 Pa (4.5 x 106psi)
Young’s Modulus 7.2 x 1010 Pa (10.5 x 106 psi)
Poisson’s Ratio 0.17
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 Point 1683°C
Annealing Point 1215°C
Strain Point 1120°C
Electrical Resistivity (350°C) 7 x 107 ohm cm
Dielectric Properties (20°C, 1 MHz)  
          Constant 3.75
          Strength 5 x 107 V/m
          Loss Factor <4 x 10-4
          Dissipation Factor <1 x 10-4
Index of Refraction 1.4585
Constringence (Nu value) 67.56
Velocity of Sound-Shear Wave 3.75 x 103 m/s
Velocity of Sound/Compressional Wave 5.90 x 103 m/s
Sonic Attentuation <11dB/m MHz
Permeability Constants (700°C) (cm3 mm/cm2 sec cm Hg)
          Helium 210 x 10-10
          Hydrogen 21 x 10-10
          Deutrium 17 x 10-10
          Neon 9.5 x 10-10
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