Taranakite: The Story of the First Mineral Described From New Zealand

Taranakite is the first of 13 minerals that have been first described from New Zealand and accepted as valid by the International Mineralogical Association. This is its story.

Taranakite is a fine-grained, cream phosphate, originally found in veins cutting volcanic rock on the tiny Sugar Loaf Islands (Nga Motu) near New Plymouth in Taranaki. It was first discovered by Henry Robert Richmond, Superintendent of the Taranaki Province (1865-1869), and then described in 1865 by James Hector (a Scottish geologist who was NZ’s leading scientist for many years, and after whom Hector’s dolphin was named) and William Skey (an analytical chemist). The details of their publication are as follows: “Taranakite, a new phosphatic mineral, Taranaki, presented by H. Richmond, Esq.” in Appendix A. Supplementary Report on Class 1. Reports of the Jurors, New Zealand Exhibition, pp. 423-425 (available online here). [The authoritative mindat.org mineral database entry on Taranakite mistakenly has “Expedition” instead of “Exhibition” in the title of this article.]

Hector and Skey wrote that chemical analysis showed this mineral to be “essentially a double hydrous phosphate of alumina and potash, part of the alumina being replaced by sesqui-oxide of iron” (pages 423-424). Such a mineral had not been reported before and the authors had named it “after the locality where it is found”. 

Te Ara The Encyclopedia of New Zealand states that Taranakite is formed by a chemical reaction between bird droppings (guano) and weathered volcanic rock. Technically, Taranakite is a “hydrated alkali iron-aluminium phosphate mineral” with the chemical formula (K,Na)3(Al,Fe3+)5(PO4)2(HPO4)6·18H2O. As wikivisually.com puts it, it forms from the reaction of clay minerals or aluminous rocks with solutions enriched in phosphate derived from bat or bird guano or, less commonly, from bones or other organic matter. It is most commonly found in humid, bat inhabited caves near the boundary of guano layers with the cave surface. It is also found in constantly wet coastal locations that have been occupied by bird colonies, such as the Sugar Loaf Islands off Taranaki where Richmond found it. 

James Hector (see photos below) had been born in Edinburgh in 1834. He graduated with a medical degree in 1856 and was then appointed doctor and geologist on the Palliser Expedition to Canada which undertook exploration for new railway routes. In 1858, while in the Canadian Rockies, his horse kicked him and he was thought to be dead. However, he revived. “Kicking Horse” Pass and River were named after this event. In 1862, he was employed to go to Dunedin in New Zealand to conduct a three-year geological survey of Otago, soon after the discovery of gold there. It was during this time that he first employed William Skey. In 1865 Hector was appointed to found the Geological Survey of New Zealand, and it was in that year that he and Skey published the discovery of Taranakite.

James Hector became widely consulted by the New Zealand government on scientific matters. He was responsible at various periods for many scientific institutions, including the Meteorological Department, the Colonial Observatory, the Wellington Time-ball Observatory and the Botanic Garden of Wellington, and for the custody of the standard weights and measures and the Patent Office library. In fact, for 40 years, he controlled virtually every aspect of state-funded science in the country. He was knighted in 1887. He retired in 1903 and died in 1907. An account of his life and work can be found in Te Ara The Encyclopedia of New Zealand.

William Skey (see photos below) was born in London in 1835 and worked in farming before coming to New Zealand with his brother in 1860. After a couple of years spent in the Otago goldfields, James Hector appointed him as laboratory assistant to the Geological Survey of Otago. In 1865, Skey moved with Hector to Wellington when the latter set up the NZ Geological Survey. He spent 35 years as chemical analyst with the Survey. His job entailed the provision of chemical analyses by which the economic potential of geological discoveries could be assessed. For example, in the article he wrote with Hector announcing the discovery of Taranakite, Skey wrote that if Taranakite “could be obtained in quantity at a reasonable expense, it would be valuable as a source of phosphoric acid for agricultural purposes” (page 424). As well as his chemical analyst work, Skey maintained a strong interest in farming, and had a small property in the Carterton area. His other major interest was poetry, writing especially parodies of Shakespeare and Milton which have been described as deliciously awful.

When Skey died in 1900, James Hector wrote in his obituary that Skey had become a world authority in many aspects of mineral chemistry and petrology (the study of rocks). This is a remarkable achievement because Skey had very little formal training, he worked extraordinarily hard for long hours and low pay, and his work was carried out essentially in isolation, in basic conditions with unsophisticated scientific instruments. He was involved in the discovery of two of New Zealand’s 13 minerals, Tarankite and Awaruite. An account of William Skey’s life and work can be found in Te Ara The Encyclopedia of New Zealand

Taranakite has now been found in a wide range of locations across the globe (see the photo below left for the localities map from Mindat). The photo of Taranakite second from left below is from Chrystalls Beach on the coast near Milton in Otago, New Zealand: “Coming from a rock-stack used by sea-birds, this cross-section of a rock, probably basalt, shows alteration to taranakite caused by the action of guano. The compact white layer at the top is the taranakite.” The photo second from right below is from Skipton Caves, Mt. Widderin, Victoria, Australia: “White chalky mass of Taranakite…on minor basalt matrix.” The photo on the far right below shows Taranakite resulting from the alteration of bat guano in the Sassyk-Unkur cave in Kyrgyzstan. Source of all four photos is mindat.org.

I have found that the best researched and most informative account of Taranakite to be the one on classicgems.net. It notes that “it is very soft…, lacks cleavage and is malleable and unctuous (having a greasy or soapy feel). Taranakite gems are extremely rare, very small and considered to be a gem collector’s oddity.”

Author: tumblestoneblog

Retired Academic, male, living in the New Zealand countryside with his wife, two cats (Ollie and Fluffy), two horses (Dancer and Penny) and a shed half-full of stones. Email john.tumblestone@gmail.com.

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