Pyrophyllite heat treated at 1250°C - 1300°C

Want to keep this datasheet? Save it now in your required format


Pyrophyllite (Aluminium silicate) is a machinable mineral which, after heat treatment, assumes many of the properties of fired ceramics. It is ideal for prototypes, experimental and pilot scale productions where high accuracy is required on small parts. When this material is heat treated it hardens and its properties change; we therefore supply Pyrophyllite in three grades:

  • The natural material. Extremely easy to fabricate, but of rather low strength.
  • Heat treated to 800 - 1000 °C. This grade is characterized by its low thermal conductivity and coefficient of thermal expansion, resulting in very good thermal shock resistance. This version of the heat-treated material can be machined to final size with tungsten carbide tools.
  • Heat treated to 1250 - 1300 °C. This grade is characterized by its excellent electrical properties, high strength and hardness. This version of the heat-treated material can only be machined with diamond tooling.

This material data has been provided by Matmatch.

"Typical" values were obtained via a literature search. "Predicted" values were imputed via artificial intelligence technology. While we have placed significant efforts in ensuring data accuracy, "typical" and "predicted" data should be considered indicative and verified by appropriate material testing. Please do contact us if additional information on the the predicted data method is required.
All metrics apply to room temperature unless otherwise stated. SI units used unless otherwise stated.
Equivalent standards are similar to one or more standards provided by the supplier. Some equivalent standards may be stricter whereas others may be outside the bounds of the original standard.

Ashby charts





23.0 °C

2.4 - 2.55 g/cm³

Show Material materials with Density of 2.4 - 2.55 g/cm³


0.01 %

Show Material materials with Porosity of 0.01 %



Compressive strength

23.0 °C

151.6 MPa

Show Material materials with Compressive strength of 151.6 MPa

Flexural strength

23.0 °C

82.7 MPa

Show Material materials with Flexural strength of 82.7 MPa

Hardness, Mohs

23.0 °C

7 [-]

Show Material materials with Hardness, Mohs of 7 [-]

Tensile strength

23.0 °C

34.4 MPa

Show Material materials with Tensile strength of 34.4 MPa



Coefficient of thermal expansion

600.0 °C

6E-6 - 8E-6 1/K

Show Material materials with Coefficient of thermal expansion of 6E-6 - 8E-6 1/K

Max service temperature

1100 °C

Show Material materials with Max service temperature of 1100 °C

Thermal conductivity

23.0 °C

1.9 W/(m·K)

Show Material materials with Thermal conductivity of 1.9 W/(m·K)

Vicat softening temperature

1600 °C

Show Material materials with Vicat softening temperature of 1600 °C



Dielectric constant

23.0 °C

5.2 [-]

Show Material materials with Dielectric constant of 5.2 [-]

Dielectric strength

23.0 °C

24 kV/mm

Show Material materials with Dielectric strength of 24 kV/mm

5mm thick test piece

Loss factor

23.0 °C

0.05 [-]

Show Material materials with Loss factor of 0.05 [-]

Power factor

23.0 °C

1000 - 1300 [-]

Show Material materials with Power factor of 1000 - 1300 [-]

Technological properties

Chemical composition

Silica - 56.8%, Alumina - 33.37%, Ferric oxide - 0.79%, Titanium Dioxide - 2.42%, Calcium Oxide - 0.29%, Magnesium Oxide - 0.24%


Pink to dark brown


Typical characteristics of the Pyrophyllite material include: Machinable, thermally insulating, good thermal shock properties, good mechanical stability once fired. The key features of Pyrophyllite Heat Treated at 1250 °C - 1300 °C are: Good electrical properties in humid conditions, high abrasion resistance, will give <3µm surface finish, high dielectric strength, fair dielectric constant, high mechanical stability, only diamond grinding can be used to adjust sizes. Over 1000 °C a gradual shrinkage takes place and the machined component loses some of the volume expansion that has occurred. As the material densifies the sizes will return to within ± 1% of the machined sizes. Any size alteration will have to be carried out by wet grinding. Diamond with coolant is best but Green grit wheels suffice on prototypes. Always allow Furnace to cool naturally to 200 °C before removing parts. Never wet the unfired material for machining. Safe maximum operating temperature 1100 °C.