Spherical Silica

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Product Description
Benefits & Application Details



Spherical silica is basically silica “shaped” in a high temperature fusion process. Spherical silica therefore has the same intrinsic properties as any other silica.

Its chemical formula is SiO2

At Sibelco, high purity silicas are being used to make spherical silica.


Quartz (silica, SiO2) is the core mineral within the Sibelco group and can be found in a broad number of applications, such as glass, ceramics, filtration, construction,….. and polymers. 


Other than fusion (to obtain spherical silica) Sibelco has other capabilities to process quartz: 

  • Classifying quartz to obtain materials with specific certain, but not milled nor calcined – the material is called Silica Sand. Products are called Silica Sand.(for more information see elsewhere in the tool under Quartz).
  • Milling, drying and classifying quartz – the material is called Quartz Flour. Products are called Silverbond (M). (for more information see elsewhere in the tool under Quartz).
  • Milling, drying and classifying  high purity quartz – the material is called Fused Silica. Products are called Megasil FS. (for more information see elsewhere in the tool under Fused Silica).
  • Calcining quartz (high temperature treatment – the crystal structure changes) – the material is called Cristobalite. If additionally milled it is called Cristobalite flour. Products are called Sibelite or Minbloc M (for more information see elsewhere in the tool under Cristobalite).


Quartz can be characterised by:

  • Relatively high Mohs hardness of 7
  • Low electrical conductivity
  • Easy to wet
  • High inertness in various media
  • Shape (depending on the source, quartz particles can have an angular or more rounded shape)


Note when using quartz: depending on the particle size distribution of the product, it can be labelled (STOT RE 2 or STOT RE 1). For more detailed information, visit  www.safesilica.eu.


Basic properties

Property Value Unit
Moisture 0.02 [%]
pH 5 [-]
Hardness (Mohs) 6 [-]
Refractive index 1.45 [-]
Density 2.20 [kg/ dm3]
Thermal conductivity 3.30 [Wm−1K−1]
CTE 0.5 x 10-6 [K-1]

Spherical Silica is mostly used in epoxy molding formulations, where it not only provides mechanical strength, but foremost provides dimensional stability (minimizing thermal stress). The sphericity of the particles allow for loadings in the epoxy-resin up to 70 – 90 %.  The sphericity of the particles also helps in processing the formulated compound in the (transfer) molding process as it improves the flowability of the material. 


These features make Spherical Silica an important raw material not only for use in semi-conductor production (EMC – packaging  / PCB – copper cladding laminate), but also in less intricate and demanding applications in adhesives and insulating materials.

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