Outstanding green sharp isolated hydrohonessite crystal on millerite from this Italian locality (Groppallo, Piacenza Province, Emilia Romagna, Italy) in a contrasting matrix. Originally described as jamborite, now most green coatings on millerite like this have been shown to be hydrohonessite. — Photo: David Hospital · CC BY-SA 4.0
Hydrohonessite
Hydrohonessite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (Ni₁₋ₓFe³⁺ₓ)(SO₄)ₓ/₂(OH)₂·nH₂O (x 3x/2).
It crystallizes in the hexagonal crystal system. It is a member of the Woodwardite, Hydrotalcite structural group.
Key properties: specific gravity 2.96; [Adamantine.] luster; optically uniaxial.
IMA symbol Hhon, IMA status: approved, named in 1980.
Incrusting fractures in the oxidized portions of Ni–Fe sulfide deposits (Otter Shoot mine and Carr Boyd mine, Australia); or in chromitite (Unst, Scotland; Linden, Wisconsin, USA).
It is found associated with Honessite, reevesite, magnesite, gaspéite, pecoraite, goethite, gypsum (Otter Shoot mine and Carr Boyd mine, Australia); honessite, reevesite.
As the hydrated analog of honessite.