The willemite is a Minéral pertaining to the family of the Silicate S (zinc silicate). Its Chemical formula is Zn₂SiO₄. The willemite belongs to the crystalline Système trigonal, its network is rhomboedric, its Groupe of space $R\; \backslash \; bar\; \{3\}$.

She was discovered in 1830 and was named in the honor of Guillaume Ier of the Netherlands ( Willem I in Dutch).

The structure consists of a three-dimensional network of tetrahedrons comprising in an ordered way two Cation S of Zinc and Silicium; it is classified among the Nésosilicate S in the classification of Machatski-Bragg, but among the Tectosilicate S in the classification of Zoltai.