- Heazlewoodite
Heazlewoodite, Ni3S2, is a rare sulfur-poor
nickel sulfide mineral found in serpentinitiseddunite . It occurs as disseminations and masses of opaque, metallic light bronze to brassy yellow grains which crystallise in thetrigonal crystal system. It has a hardness of 4 and a specific gravity of 5.82.Paragenesis
Heazlewoodite is formed within terrestrial rocks by
metamorphism ofperidotite anddunite via a process of nucleation. Heazlewoodite is the least sulfur saturated of nickel sulfide minerals and is only formed via metamorphicexsolution of sulfur from the lattice of metamorphicolivine .Heazlewoodite is thought to form from sulfur and nickel which exist in pristine olivine in trace amounts, and which are driven out of the olivine during metamorphic processes. Magmatic olivine generally has up to ~4000ppm Ni and up to 2500ppm S within the crystal lattice, as contaminants and substituting for other
transition metal s with similar ionic radii (Fe2+ and Mg2+).During metamorphism, sulfur and nickel within the olivine lattice are reconsitituted into metamorphic sulfide minerals, chiefly
millerite , duringserpentinization andtalc carbonate alteration.When metamorphic olivine is produced, the propensity for this mineral to resorb sulfur, and for the sulfur to be removed via the concomittant loss of volatiles from the serpentinite, tends to lower sulfurfugacity .In this environment, nickel sulfide mineralogy converts to the lowest-sulfur state available, which is heazlewoodite.
Heazlewoodite is also known to occur within meteorites in association with
troilite andtaenite .Occurrence
Heazlewoodite is known from few ultramafic intrusions within terrestrial rocks. The Honeymoon Well ultramafic intrusive,
Western Australia is known to contain heazlewoodite-millerite sulfide assemblages within serpentinised olivine adcumulate dunite, formed from the metamorphic process.The mineral is also reported, again in association with millerite, from the ultramafic rocks of
New Caledonia .Heazlewoodite was first described in 1896 from Heazlewood,
Tasmania , Australia.See also
*
Serpentinite
*Metamorphism
*Olivine
*Dunite orperidotite
*Millerite
*Polydymite
*Vaesite References
* Guillon J.H. and Lawrence L.J., The opaque minerals of the ultramafic rocks of New Caledonia, "Mineralium Deposita", volume 8, 1973, pp. 115-126.
* [http://webmineral.com/data/Heazlewoodite.shtml Webmineral data]
* [http://www.mindat.org/min-1839.html Mindat with location data]
* [http://rruff.geo.arizona.edu/doclib/hom/heazlewoodite.pdf Mineral Data Publishing - PDF]
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