Taranakite is a hydrated aluminium
phosphate mineral which is a secondary mineral formed from
phosphatic solutions derived from bird or bat guano
reacting with clays or aluminous rocks under perenially
damp conditions in caves and along sea coasts. Taranakite forms as
very small white, pale yellow or gray crystals, which are typically found in
nodular aggregates or crusts. It is very soft, with
a Moh's hardness of 1 - 2, lacks cleavage and is malleable
and unctuous (having a greasy or soapy feel). Taranakite gems are extremely rare,
and considered to be a gem collector's oddity.
Taranakite crystallizes in the hexagonal system
and until 2009, was noted as having the longest crystallographic axis of any known mineral; the c-axis of the Taranakite unit cell is
95.05 Angstroms (9.505 nanometers) long. In 2009
however, Byzantievite was approved as a new mineral
having a c-axis of 102.145 Angstroms (10.214 nanometers)
is also noted as being the first new mineral to be discovered
in New Zealand. It was discovered in 1865 by Henry Robert
Richmond (1829-1890), fourth superintendent of Taranaki, on the Sugar Loaf Islands of Taranaki, New Zealand.
Taranakite was first analyzed and described by Scottish
geologist Sir James Hector (1834-1907),
and English analytical chemist William Skey (1835-1900). It
was initially mistaken for Wavellite but
was found to be a new mineral after analysis by Hector
and Skey. James Hector was the first Director of New
Zealand's Colonial Museum and Laboratory, with
William Skey as its first analyst.
Taranakite was later "rediscovered" in two cave locations and given two new
names. In 1894, Armand Gautier described a mineral which he called "Minervite" from caves at
Grotte de Minerve in Hérault, France
and argued that it formed from decomposing guano and animal remains
reacting with clays. In 1904 Eugenio Casoria found a mineral under a guano layer at
Monte Alburno, Italy which he called "Palmerite"
after Italian Professor Paride Palmeri, American Academy, Rome, Italy. These two minerals were later identified through
X-ray powder diffraction as Taranakite and discredited in favor of Taranakite by historical priority.
from the Sugar Loaf Islands, near New Plymouth, Taranaki
Peninsula, New Zealand. On Réunion Island, Indian Ocean;
Island Leones, Patagonia, Argentina; King George Island,
Maritime Antarctic. In Australia, in the Russenden Cave,
Queensland; the Skipton lava tube caves, 40 km southwest
of Ballarat, Victoria; in caves at Mimegarra, Western
Australia; and the Jenolan Caves, New South Wales. In
the Yangsue Posayen Cave, 20 km south of Guilin, Guangxi
Province, China. From the Niah Great Cave, Sarawak,
Malaysia. In the Onino-Iwaya Cave, Hiroshima Prefecture,
Japan. From the Tour Combes Cave, near Oran, Algeria.
In Etienne’s Cave, and well-crystallized in Christmas
Cave, Transvaal, South Africa. From the Bacho Kuo Cave,
Bulgaria. In the Minerva Grotto, Fauzan, Hérault, France.
In Italy, in the Castellana Cave, south of Bari, Puglia;
on Monte Alburno, near Controne, Salerno. In the USA,
in the Pig Hole Cave, Giles County, Virginia; and the
Low Water Bridge Cave, Greene County, Missouri. Additional
localities are known.