Story: Rock and mineral names
Page 3 – Mineral names – 1
Thirteen minerals, all named after local features or people, have been named from New Zealand, and most have since been identified overseas. Seven of the mineral names are derived from Māori place names from where the minerals were first discovered. Four are modifications of existing mineral names, and two are named after local mineralogists.
To avoid duplication, proposed new mineral names need to be approved by the International Mineralogical Association. Proposals are checked to ensure that a mineral is indeed new. The minerals listed below have all been accepted by the association.
Taranakite – KAl3(PO4)3(OH)9H2O
In 1886 James Hector (a geologist) and William Skey (an analyst) described taranakite – the first new mineral to be identified in New Zealand. It is a fine-grained, cream phosphate, originally found in veins cutting volcanic rock in the Sugar Loaf Islands near New Plymouth in Taranaki.
Taranakite forms by a chemical reaction between bird droppings (guano) and weathered volcanic rock. It has since been found in coastal localities, in New Zealand and overseas, where bird droppings accumulate.
Awaruite – Ni2Fe to Ni3Fe
This natural nickel-iron alloy was originally found as water-worn grains in the Gorge River, South Westland. It was identified by William Skey in 1886, and traced back to serpentinite in the Cascade Valley. It has since been found in serpentinites throughout the world.
The name is slightly misleading as the mineral does not occur in the Awarua River or Awarua (Big) Bay.
Searching for Tuhualite
The British aviator and yachtsman Francis Chichester joined an expedition organised by Patrick Marshall to look for tuhualite on Mayor Island as cook. His culinary standard was not high, and he recalled:
One day I grilled some steaks from a 150-lb swordfish; I must admit they were pretty tough. We had two professors in the party, and they had a dispute; one of them got so angry that he picked up a loaf of bread to hurl it at the other. He was so furious that when he drew back his hand to hurl the loaf it flew out backwards; when his hand came forwards there was nothing in it. I thought that this was the funniest thing I had seen for years, and doubled up with laughing. Whereupon they both turned on me and said that it was entirely my fault; that my bad cooking had upset their livers. 1
Tuhualite – (Na,K)Fe2Si6O15
Unique to New Zealand, tuhualite was identified by geologist Patrick Marshall in 1932. It is a rare constituent of the distinctive alkali rhyolites of Tūhua (Mayor Island) in the Bay of Plenty. It has also been recorded in volcanic ash on the Coromandel Peninsula, derived from Tūhua. Tuhualite occurs as isolated, tiny violet to deep purple crystals, up to 0.25 millimetres long.
Hydrogrossular – Ca3Al2(SiO4)3-x(OH)4x
In 1943 mineralogist Colin Hutton gave the name hydrogrossular to a calcium-rich variety of garnet that is the main constituent of the rock rodingite, also named from New Zealand. As the name indicates, it contains some water. Recent research has shown that most of what was previously described as grossular garnet contains some water, and is better described as hydrogrossular.
Hydrogrossular ranges from yellowish brown to pale green. Rounded pebbles are found on some Southland beaches, and it has been used for carving.
Huttonite – ThSiO4
As part of a government-funded search for radioactive minerals in the 1940s, Colin Hutton undertook a detailed survey of beach sands in South Westland. He identified a rare, highly radioactive mineral which he described as a uranium-free variety of thorite. It was recognised as a distinct mineral by A. Pabst, who named it huttonite. It is recognised worldwide as a rare radioactive mineral.