Hörnesite

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.

Hörnesite
General
Category	Arsenate minerals
Formula	Mg3(AsO4)2·8H2O
Strunz classification	8.CE.40
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	C2/m
Unit cell	a = 10.262, b = 13.442 c = 4.741 [Å]; β = 104.9°; Z = 2[1]
Identification
References	[1]