A transition of a crystalline structure into one or more forms which differ in the way identical layers of atoms are stacked. Example: $\ce{ZnS}$ consists of two identical close packings, one of $\ce{Zn}$ atoms, the other $\ce{S}$ atoms, with the one displaced to the other along the c-axis through one-quarter of the layer spacing. In sphalerite-type $\ce{ZnS}$ the layers have the face-centred-cubic (ABC ABC) sequence, in wurtzite-type $\ce{ZnS}$ they have the hexagonal-close-packed (AB AB) sequence. The transition of sphalerite-type $\ce{ZnS}$ to wurtzite-type $\ce{ZnS}$ occurs at \(1297\ \rm{K}\).