Morenosite

morenosite

retgersite

nickelhexahydrite

millerite

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Formula: Ni(SO4).7H2O
Hydrated normal sulphate, epsomite group, forms a complete series with epsomite, nickel-bearing mineral
Specific gravity: 1.953
Hardness: 2 to 2½
Streak: White, faint green tint
Colour: Apple green or greenish white, green in transmitted light
Common impurities: Fe
Environments

Hydrothermal environments

Morenosite is an uncommon secondary mineral in the oxidised zone of nickel-bearing hydrothermal mineral deposits, formed from H2O solution below 31.5oC. Associated minerals include retgersite, nickelhexahydrite, annabergite and millerite (HOM).

Localities

At Marbridge Mine, La Motte, Abitibi RCM, Abitibi-Témiscamingue, Quebec, Canada, morenosite is found coating millerite (Dana).

At Malenco Valley, Sondrio Province, Lombardy, Italy, morenosite is associated with retgersite (Dana).

At the Ragra mine (Minasragra), Huayllay District, Pasco Province, Pasco, Peru, morenosite has been found associated with minasragrite and retgersite on a specimen of patronite (AM 34.188-194).

At the type locality, the Manolita mine, Teixidelo, Cedeira, A Coruña, Galicia, Spain, morenosite commonly occurs as fibrous or fine-grained efflorescences and contains hydrous impurities, notably annabergite (AM 34.188-194).

At Gordon's Quarry, Kaukapakapa, Auckland Region, North Island, New Zealand, morenosite is found as efflorescent patches on freshly broken surfaces of serpentinite. The host rock is a serpentinite of the dunite type enclosing scattered grains of pentlandite-bearing pyrrhotite, and it is on these that morenosite has crystallised. In the same quarry epsomite also occurs at other points on the serpentinite surface. The close association of the morenosite and epsomite with pyrrhotite suggests that the pyrrhotite was a factor in their formation. Oxidation of pyrrhotite gives ferric sulphate and sulphuric acid; the sulphuric acid so derived reacts with the readily soluble serpentinite and with the pentlandite in the pyrrhotite, giving sulphates of nickel, magnesium, and iron (AM 32.553-560).

Alteration

Morenosite dehydrates to retgersite
Ni(SO4).7H2O → Ni(SO4).6H2O + H2O

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