 At low temperatures, there is not enough energy for the crystal grains to deform plastically, thus each grain fractures as opposed to elongation or recrystallizing.In these systems, cataclasites would be more likely to form as opposed to mylonites, which would require crystal plastic deformation.Due to quartz being the main mineral in many rocks in the brittle regime of the crust, the brittle-ductile transition for quartz can be a good indication of where cataclasites would form before ductile deformation plays a role.