Stacking faults and twins in kyanite, Al2SiO5

Abstract

Two types of twins are frequently found in naturally and experimentally deformed kyanite. Structural models based on periodic shears are proposed to account for these mechanical twins. The structure of kyanite is then regarded as layered, the limits of each layer being easy glide planes for dislocations. The shear plane is (100). The shear vectors are ½ [001] and ½ [011]. They are suitable for the only known glide system (I00)[001].