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Atomic Positional Parameters
Si(1) 6f 0.4590 0.2250  0.0510
Zn(1) 6f 0.7930 0.5620  0.3850
Zn(2) 6f 0.1280 0.8970  0.7200
O(1)  6f 0.3290 0.0190 -0.0270
O(2)  6f 0.6140 0.3070  0.2580
O(3)  6f 0.9710 0.6390  0.6400
O(4)  6f 0.5530 0.2290 -0.0920

Reference
Hang C, Simonov MA and Belov NV (1970) Kristallografiya 15 457

Mineral Chemistry
An ore of zinc, willemite is found in oxidised zones of zinc deposits and in metamorphosed environments - it may be formed from the metamorphism of hemimorphite. A locality for willemite is Franklin, New Jersey, USA.

Willemite belongs to the phenakite (Be₂SiO₄) group. In willemite, both zinc and silicon are tetrahedrally coordinated by oxygen. Under ultra-violet light, willemite shows strong green fluorescence. Replacement of zinc by manganous and ferrous ions forms the mineral troostite.

The CHIME figure shows zinc ions as brown spheres, oxygens as red spheres and silicons as ochre spheres. The unit cell is outlined.