Millerite

sulphide

hydrothermal

Formula: NiS Sulphide
Specific gravity: 5.3
Hardness: 3½
Streak: Dark green
Colour: Brass-yellow
Solubility: Insoluble in hydrochloric acid and sulphuric acid; moderately soluble in nitric acid
Environments:

Hydrothermal environments

Millerite forms as a low-temperature mineral often in cavities and as an alteration of other nickel minerals, or as crystal inclusions in other minerals. Millerite occurs in nickel deposits, as an alteration product of other nickel ores.

At Fall Hill quarry, Ashover, Derbyshire, England, UK, millerite has been found on calcite (RES p104).

At the Linton quarry, Gorsley Common, Herefordshire, England, UK, millerite has been found associated with galena (RES p181).

At the Clayton adit, Ecton mine, Staffordshire, England, UK, millerite has been found on calcite (RES p308).

Common impurities: Fe,Co,Cu

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