Formula: (Ni1-xFe3+x)(SO4)x/2(OH)2.nH2O (x < 0.5, n < 3x/2)
Hydrated sulphate containing hydroxyl, woodwardite group, nickel-bearing mineral
Hardness: 1 to 1½
Streak: Brownish white
Colour: Green, brown
Solubility: Insoluble in water. Soluble with slight effervescence in dilute acid solutions. Free oxygen is liberated (Mindat)
Honessite is derived from the oxidation of millerite and other
primary nickel sulfides
(Webmin). It may convert readily into hydrohonessite, depending on
humidity and temperature
At Hagdale Quarry, Unst, Shetland Islands, Scotland, UK, honessite occurs on nickel-bearing chromite associated with reevesite, hydrohonessite and theophrastite (HOM, Dana).
At the type locality, Linden, Upper Mississippi Valley Mining District, Iowa county, Wisconsin, USA, honessite occurs as a green or brown powdery alteration of millerite, associated with millerite, violarite and bravoite (HOM).
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