Are all minerals brittle

Answer 1

This depends on the confining pressure, the temperature and the strain rate applied to the mineral.

In general for minerals (and other materials), the lower the rate of strain, the more likely ductile or plastic creep deformation will occur. The higher the strain rate, the more likely brittle deformation is to occur.

As the confining pressure increases, an objects shear strength will increase (this usually coincides with a greater depth of burial) and due to the earth's thermal gradient an increase in temperature.

As the shear strength increases, brittle failure is less likely and the higher temperature means that plastic deformations or creep are more likely to occur.

Answer 2

No, not all minerals are brittle. While many minerals are indeed brittle, such as quartz and calcite, some minerals like mica and talc exhibit a more flexible or elastic behavior. Minerals can vary in their physical properties, including their toughness and resistance to breaking.