A transition of a crystalline structure into one or more forms which differ in the way identical layers of atoms are stacked. Example: ZnS consists of two identical close packings, one of Zn atoms, the other S atoms, with the one displaced to the other along the c-axis through one-quarter of the layer spacing. In sphalerite-type ZnS the layers have the face-centred-cubic (ABC ABC) @ST06775@, in wurtzite-type ZnS they have the hexagonal-close-packed (AB AB) @ST06775@. The transition of sphalerite-type ZnS to wurtzite-type ZnS occurs at \(1297\ \text{K}\).