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Product Description
Benefits & Application Details


Cristobalite (silica, chemical formula SiO2) is the result of the calcination of quartz at a temperature of 1500°C.



Cristobalite can be characterised by:

  • High brightness
  • Relatively high Mohs hardness of 6.5
  • Relatively low refractive index, making it a transparent filler in various binders
  • Easy wetting
  • High inertness in various media
  • Transparency for UV-radiation (ie. suitable for UV-curing processes)


Note when using cristobalite: 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


Basic properties

Property Value Unit
Moisture [%]
pH 9 [-]
Hardness (Mohs) 6.5 [-]
Refractive index 1.48 [-]
Colour (D65/ 10°) L* 98 [-]
Density 2.3 [kg/ dm3]


Sibelite is the product name for Sibelco’s cristobalite products. Minbloc M is the product name for film additives based on Sibelco cristobalite.

The finer Sibelite grades are mostly used in Sealant and Adhesives  as an extending filler to reduce formulation cost. They can depending on formulation also have an effect on surface texture, durability (UV resistance)  and chemical resistance. Sibelite grades can also be used in UV curing systems

The majority of the fine grades are labelled STOT RE 2 or STOT RE 1 due to the presence of fine crystalline silica.


 MINBLOC® materials are used as film anti-block additives offering the following features:

  • Anti-blocking
    • To overcome the blocking phenomenon, MINBLOC® M additives may be added to create a micro surface roughness with particles protruding from the smooth film surface.

Without MINBLOC® M                       With MINBLOC® M


  •  MINBLOC®  M grades are made in dedicated locations which meet the stringent global regulatory requirements. As such our additives have found worldwide regulatory acceptance as so called “indirect food contact additive’s” for plastic film.
  • MINBLOC® M grades have a refractive index close to that of polyolefin resulting in a high transparency and clarity films
  • MINBLOC® M grades have low surface area (m2/g) leading to Low Absorption of other additives and consequently cost-savings

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