The Mineral Millerite
millerite mineral picture

millerite picture

Millerite appears as a brassy colored mineral of nickel sulfide (NIS.) leading to the formation of furry aggregates or radiating masses of acicular habit. It is different due to its crystal habit from Pentlandite.  It does not associate with Pyrrhotite or Pyrite due to its dull color. "Capillary Pyrite" is another name given to Millerite due to its color configuration of brassy yellow, that is nearer Pyrite’s color and forms crystals of the trademark capillary structure. Millerite is extremely attractive when sourced from inside quartz geodes in the form of brassy sprays.
Chemical Configuration

Derivation of Name  
Wilhelm Haidinger discovered Millerite in 1845 in the coal mines of Wales. It was named after William Hallowes Miller, a mineralogist in Britain.

Millerite occurs in the form of a metamorphic substitute of Pentlandite within the nickel deposits at Silver Swan, Western Australia, and all through the several ultramafic serpentinite representations in the Yilgarn Craton, in Western Australia, usually as a substitute of metamorphosed pentlandite. It normally occurs as a radiating bunch of needle-like acicular crystals in sulfide rich dolomite’s cavities and limestone’s or in the geode’s cavities. It also occurs in meteorites of nickel-iron like CK carbonaceous Chondrites.            

Some collectors cut huge Millerite to a cabochon or slice them into slabs for decorative applications. Its rich yellow color is striking and the cut gems have a curious appearance. It is too soft to be worn. Large chunks of the mineral are of no interest to collectors and thus difficult to procure in the market, though it is available in abundance in certain areas.

It’s rare to get a specimen of this mineral. It is mostly found in the Halls Gap area of Lincoln County, Kentucky, in The United States. 
Millerite is a significantly found as ore bodies in Honeymoon Well, Yakabindie; Silver Swan, Wannaway, Cliffs and Mt Keith (MKD5).  It is an accomplice mineral linked to Nickel Laterite deposits in New Caledonia.

Millerite of high concentration represents a significant nickel ore because, being a mineral of sulfide, it displaced a higher nickel percentage than Pentlandite. In other words, it only means that,   for a given volume of Millerite, the ore contains more nickel than Pentlandite sulfide.

Pale brass-yellow to bronze-yellow, tarnishes to iridescence               

5.3 - 5.5 g/cm3

Mohs hardness         
3 - 3.5

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