Thirteen minerals have been first described from New Zealand and accepted as valid by the International Mineralogical Association. Hydrogrossular is the fourth one to have been so discovered. In a previous Post, I said I would look at these minerals. Simon Nathan has provided a list of the 13 on the website of the Geoscience Society of New Zealand. There are more informative comments by Nathan on them in Te Ara The Encyclopedia of New Zealand. Two very useful if more technical sources are Mindat.org, a non-commercial online mineralogical database (the world’s largest), and rruff.info, an integrated database of the chemistry, crystallography, x-ray and other analytical data about minerals. Rruff.info also includes online versions of important publications on different minerals.
A mineral is a naturally occurring inorganic solid, with a definite chemical composition, and an ordered atomic arrangement. Often the best way for a mineral to form is through the cooling of very hot water or other fluid which contains it in solution. A rock is made up of one or more minerals, most often more than one. In a rock, mineral grains are fused, cemented or bound together. For example, granite is a rock primarily composed of three minerals – quartz, mica and feldspar. The crystals of these three minerals interlocked during the cooling of molten magma. The quartz is grey and glassy, the feldspar is light, often in prismatic crystals, and the mica is glittery, being dark or silvery in colour.
The following are the 13 New Zealand-origin minerals in the order in which they were discovered:
1) “Taranakite” (above left) is a fine-grained cream-coloured phosphate first described in 1865 by James Hector (NZ’s leading scientist at the time) and William Skey (an analytical chemist). It was named after the Province of Taranaki as it was first found on small islands near New Plymouth in that Province.
2) “Awaruite” (above middle), a natural nickel-iron alloy, was first described in 1885 by William Skey (mentioned in #1 above). It had been obtained from gold miners south of Haast on the West Coast of the South Island, around the Gorge River, and was named after nearby Awarua/Big Bay.
3) “Tuhualite” (above right), a violet crystal that is unique to New Zealand, was first identified by geologist Patrick Marshall in 1932. He had found it on Tuhua/Mayor Island in the Bay of Plenty, its only source.
4) “Hydrogrossular” (above left) is a calcium-rich garnet that was first described by Colin Hutton, a geologist and later professor of mineralogy, in 1943. He analysed samples of the rock from the Nelson area. The presence of water and thus hydroxide in its chemical make-up led to its naming. (See previous Post.)
5) “Huttonite” (above middle) is a radioactive cream–coloured crystal, first discovered in beach sands from the West Coast by Colin Hutton (see #4 above) who sent it to Adolf Pabst, an American mineralogist, to analyse. It was first described in publication in 1951 by Pabst who named it in honour of Hutton.
6) “Wairakite” (above right) is a colourless to white crystal found in geothermal environments. It was discovered and named in 1955 by Alfred Steiner, a pioneer geothermal scientist. He had found it while examining hydrothermally altered drill cores at Wairākei in the course of exploration for geothermal steam.
7) “Wairauite” (above left) was announced in 1964 by G.A. Challis and J.V.P. Long who worked in the Department of Mineralogy and Petrology at the University of Cambridge. It is a natural cobalt-iron alloy and was discovered by electron micro-probe analysis of Awaruite (#2 above). Wairauite occurs as microscopic, scattered grains in serpentinite, often alongside Awaruite, the grains rarely exceeding 5 microns (0.005 millimetres), so electron micro-probe is the only way to see it. It is named Wairauite as the grains initially analysed were found in the Red Hills serpentinites of the Wairau Valley in Marlborough. [Serpentinite is a rock composed of one or more serpentine group minerals, the name originating from the similarity of the texture of the rock to that of the skin of a snake.] [An electron micro-probe is an analytical tool used to non-destructively determine the chemical composition of small volumes of solid materials. It works similarly to a scanning electron microscope.]
8) “Akatoreite” (above middle) is a fibrous yellow-orange to orange-brown mineral recognised by Peter Read and Tony Reay (geologists from Carleton University and the University of Otago respectively). It is a previously unknown manganese silicate mineral. They reported in their 1971 publication that the mineral was found in a manganese-rich patch of chert and carbonate on the South Otago coast, three kilometres south of the mouth of the Akatore Creek, about 12 kilometres east of Milton.
9) “Motukoreaite” (above right) is a poorly cemented fine-grained calcareous rock that occurs on Browns Island/Motukorea in the Waitematā Harbour, Auckland. The rock was first noted in 1941 by John Bartrum, a Professor of Geology, who called it “beach limestone”. It was not officially described and named as Motukoreaite until 1977 in an article by Kerry Rogers (University of Auckland), James Chisholm (British Museum), R.J. Davis (British Museum) and Cam Nelson (University of Waikato). It occurs as a boxwork of tiny crystals, each about 3 microns (0.003 millimetres) across. The crystals are semi-transparent and are white, pale yellow, pale yellow-green, or colourless.
10) “Feruvite” (above far left) is a dark brownish-black iron-rich variety of tourmaline found in a coarse-grained granitic rock on Cuvier Island/Repanga. The island is located 23 kilometres south-east of Great Barrier Island, a similar distance to the north-east of Coromandel Peninsula. Philippa Black from the University of Auckland had noted the occurrence of a iron-rich tourmaline on Cuvier in 1971. She later provided specimens to Joel Grice and George Robinson of the National Museum of Natural Sciences, Ottawa, who found they contained this previously unknown mineral. Grice and Robinson published their discovery in 1989. The mineral is part of the uvite group, and as it is rich in iron (Fe), it was named Feruvite.
11) “Coombsite” (above second from left) consists of tiny brownish-yellow fibrous crystals. These were found in brown patchy aggregates from a small area of manganese-rich rock at Watsons Beach on the South Otago coast (only about 3.5 kilometres south of where Akatoreite is found). Two Japanese mineralogists, Teruhiko Sameshima and Yosuke Kawachi, discovered this new manganese mineral and described it in 1991. They named it in honour of Douglas Coombs, Professor of Geology at the University of Otago. Coombsite is very rare and has been found in only three localities worldwide, in New Zealand, Brazil and Romania.
12) “Ferroceladonite” (above second from right) and 13) “Ferroaluminoceladonite” (above far right) were discovered in the 1990s when crystals from the Hokonui hills, east of Gore, were analysed by electron micro-probe. Previously the crystals had been identified as celadonite, a well-known mica group mineral found in altered volcanic rocks. However, the micro-probe analysis revealed two new minerals, which were named Ferroceladonite and Ferroaluminoceladonite. The crystals are extremely small, only 1 to 2 microns thick. A publication authored by Gejing Li, Donald Peacor, Douglas Coombs and Yosukee Kawachi identified these two minerals in 1997. Ferroceladonite is clay-like, usually green, and includes fine coatings and powdery masses. It was named for its ferrous content and its relation to celadonite. Ferroaluminoceladonite was also reported to be usually green in colour, is described as earthy, and its name reflects the significance of the presence of aluminium.
Future Posts may look at some of these minerals and their discovery in more detail. The first is Taranakite: The Story of the First Mineral Described From New Zealand. The second is Awaruite: The Story of the Second Mineral Described From New Zealand.
TumbleStone 
