| Hörnesite | |
| Category: | Arsenate minerals |
| Strunz: | 8.CE.40 |
| System: | Monoclinic |
| Class: | Prismatic (2/m) (same H-M symbol) |
| Symmetry: | C2/m |
| Unit Cell: | a = 10.262, b = 13.442 c = 4.741 [Å]; β = 104.9°; Z = 2 |
| References: | [1] |
Hörnesite is an arsenate mineral bearing magnesium. It is a member of the vivianite group of minerals, and constitutes the magnesium endpoint of a mineral series with nickel or cobalt replacing the magnesium, ending in annabergite or Erythrite.