Examination of quartz from plutonic source rocks, sediments and soils, using both optical and scanning electron microscopes, reveals that the mineral is, almost always, cut by sets of partially healed, subplanar, subparallel microfractures dividing it into sheets typically one to a few micrometres thick. The structure, which originates in source rocks, is not due to crystal cleavage although it does show weak crystallo‐graphic influence in its directions. One to several sets of microfractures, intersecting at varying angles, can be present in any one quartz crystal. The microfractures vary in quality like cleavages; separation takes place readily along some, less so along others.