Taranakite  Taranakite is a hydrated alkali iron-aluminium phosphate mineral with chemical formula (,)3(,3+)5(PO4)2(HPO4)6·18H2O. 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. Taranakite is most commonly found in humid, bat inhabited caves near the boundary of guano layers with the cave surface. It is also found in perennially wet coastal locations that have been occupied by bird colonies. The type location, and its namesake, the Sugar Loaf Islands off Taranaki, New Zealand, is an example of a coastal occurrence. Taranakite forms small white, pale yellow, or gray crystals, which are typically found in pulverulent nodular aggregates, or crusts. Taranakite crystallizes in the hexagonal system, and is noted as having the longest crystallographic axis of any known mineral: the "c"-axis of the taranakite unit cell is 9.505 nanometers long. Taranakite was first described in 1866 by James Hector and William Skey. The material had been found by H. Richmond on the Sugar Loaf Islands of Taranaki, New Zealand (in the vicinity of ), as thin yellowish-white amorphous seams in fissures within trachytic rocks. Within the taranakite, dark yellow-brown seams were observed and thought to be wavellite. Modern X-ray analysis later showed this inclusion to be vashegyite (Al11(PO4)9(OH)6)·38H2O). Taranakite itself was initially mistaken for wavellite. Physical differences—its relative softness and ease of fusibility—led Skey, the colonial New Zealand Government analyst, to undertake quantitative chemical analysis which identified the mineral as a double hydrous phosphate of aluminia and potash, with some replacement of aluminium with ferric iron. This identified it as a new mineral species – the first to be discovered in New Zealand. Hector and Skey identified bird guano as the most likely source of the phosphate required to form taranakite, and speculated on possible advantages of its use in making superphosphate, owing to the absence of carbonate and relatively small amounts of aluminium. Such industrial use was never realized owing to the limited distribution of taranakite.