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Mechanical Properties of Fused Quartz

Mechanical properties of fused quartz are much the same as those of other glasses. The material is extremely strong in compression, with design compressive strength of better than 1.1 x 109 Pa (160,000 psi).

Surface flaws can drastically reduce the inherent strength of any glass, so tensile properties are greatly influenced by these defects. The design tensile strength for fused quartz with good surface quality is in excess of 4.8 x 107 Pa (7,000 psi). In practice, a design stress of  0.68 x 107 Pa (1,000 psi) is generally recommended.

To discover how Momentive's fused quartz compare to synthetic fused silica, click here


Typical Physical Properties of Fused Quartz 




2.2 x 103 kg/m3


5.5 - 6.5 Mohs' Scale
570 KHN 100

Design Tensile Strength

4.8 x 107 Pa (N/m2) (7,000 psi)

Design Compressive Strength

Greater than 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 106 psi)

Young's Modulus

7.2 x 1010 Pa (10.5 x 106 psi)

Poisson's Ratio


Coefficient of Thermal Expansion (20 °C - 320 °C)

5.5 x 10-7 cm/cm • °C

Thermal Conductivity at 20°C

1.4 W/m • °C

Specific Heat at 20 °C

670 J/kg • °C

Softening Point

1683 °C

Annealing Point

1215 °C

Strain Point

1120 °C

Electrical Resistivity  at 350 °C

7 x 107 Ω • cm

Dielectric Properties at 20 °C and 1 MHz






5 x 107 V/m

Loss Factor


Less than 4 x 10-4

Dissipation Factor


Less than 1 x 10-4

Index of Refraction


Constringence (Nu value)


Velocity of Sound-Shear Wave

3.75 x 103 m/s

Velocity of Sound/Compression Wave

5.90 x 103 m/s

Sonic Attentuation

Less than 11 db/m MHz

Permeability Constants at 700 °C

(cm3 mm/cm2 sec. cm of Hg)



210 x 10-10



21 x 10-10



17 x 10-10



9.5 x 10-10




























































Typical properties are average data and should not be used as or to develop product specifications.

For more information regarding the use guidelines for fused quartz, click here.