Awaruite, a controversial and almost extraterrestrial mineral

Awaruite is a rare terrestrial nickel-iron alloy, with the formula Ni3Fe, which was found, in the form of nuggets, in black sands and of great specific weight in the Gorge River, on the West Coast of New Zealand.

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The species was determined by W. Skey, a researcher of the New Zealand Geological Survey Office, in 1885. His analytical results indicated it was this rare alloy, with an element composition more typical of meteorites than terrestrial rocks. The samples those Skey studied, came from a collection of minerals sent by the Warden of the Jackson’s Bay District (Okahu in Māori), also on the West Coast of New Zealand.

Unfortunately, Skey and his director J. Hector did not know the exact location of the founding of these black sands. The information accompanying samples indicated that they had been brought by placer gold prospectors from Barn Bay.

They gave it the name of Awaruite after Awarua Bay (Māori name for Big Bay), where the Awarua River flows out, thinking that this was the correct locality. This mineral has never been found in that bay. All samples came from the Gorge River area, about 15 km north of Big Bay and about 20 km south of Barn Bay.

View of the Gorge River mouth, West Coast, New Zealand. © Long family, Gorge River. (Font)

To add more historical interest to the species, in 1890 another researcher, G.H.F. Ulrich, tried to clear up this confusion, but received harsh criticism and allegations of plagiarism from J. Hector.

Furthermore, Ulrich indicated that Skey was wrong in considering that this nickel-iron alloy was the second mineral species with this composition and terrestrial origin found to date. Skey considered Oktibbehite (a variety of nickel, a mixture of taenite, awaruite and other Ni minerals, found in Oktibbeha Co., Mississippi, USA) to be of terrestrial origin, when in fact it was remnants of an “iron” meteorite.

Awaruite nuggets are accompanied by small crystals of magnetite, clinozoisite, zircon and epidote, along with gold, among other minerals. Later studies carried out by Ulrich showed that the highest concentrations of awaruite nuggets are found in the sands of rivers flowing between mountainous regions with outcrops of serpentinized peridotites and ophiolites.

Black “heavy” sands from Gorge River. ©Joan Rosell. (Font)

Awaruite is also known by the name of “josephinite”, after the North American locality of Josephine Creek, in Josephine-Jackson Co., Oregon, where nuggets up to “100 pounds” (sic) in weight were found (Schmeltz, 1931).

This terrestrial mineral, with an almost "extraterrestrial" composition but very rare in meteorites, has been found in several worldwide other deposits, once it was known what type of rocks you should search.

Acknowledgements

To the Long family from Gorge River (New Zealand) for the area photos.

BIBLIOGRAPHY

• Fred W. Schmeltz (1931): “Interesting localities and how to reach them: Josephine Creek, Oregon”. Rocks & Minerals, 6, 3: 142.

• Hector, J. (1887): “Oktibehite or Awaruite?”. Nature, 35: 513-514.

• Rodgers, K.A., Hey, M.H. (1980): “On the type locality and other occurrences of awaruite (FeNi3) in Westland, New Zealand”. Mineralogical Magazine, 43: 647-650. [online, Jan. 2021]

• Skey, W. (1885): “On a new mineral (awaruite) from Barn Bay”. Transactions and Proceedings of the New Zealand Institute, 18: 401-402. [online, Jan. 2021]

• Ulrich, G.H.F. (1890): “On the discovery, mode of occurrence, and distribution of the nickel-iron alloy awaruite, on the West Coast of the South Island of New Zealand”. Quarterly Journal of the Geological Society, 46 (1-4): 619-NP.