Taranakite
Current inventory:  1 gem
 

  
Taranakite is named after its disovery locality of the Sugar Loaf Islands, off Taranaki (now Port Taranaki), New Zealand.

Discovered in 1865;   IMA status:  Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

K₃Al₅(PO₄)₂(PO₃OH)₆ •18H₂O

Hydrated Potassium Aluminum Phosphate Hydroxide

Molecular Weight:

1342.30 gm

Composition:

Potassium

8.74 %

K

10.53 %

K₂O

Aluminum

10.05 %

Al

18.99 %

Al₂O₃

Phosphorus

18.46 %

P

42.30 %

P₂O₅

Hydrogen

3.15 %

H

28.18 %

H₂O

Oxygen

59.60 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Phosphates

Strunz 8th Ed. ID:

7/C.21-20

Nickel-Strunz 10th Ed. ID:

8.CH.25

8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H₂O
H : With large and medium-sized cations, RO₄:H₂O < 1:1

Related to:

n/a

Varieties:

None

Synonyms:

Minervite, Palmerite

Crystal Data

Crystallography:

Trigonal - Hexagonal Scalenohedral

Crystal Habit:

Pseudohexagonal platy crystals, rarely to 0.5 mm; typically in compact nodular aggregates, pulverulent, powdery, flourlike to claylike, massive.

Twinning:

None

Physical Properties

Cleavage:

None

Fracture:

n/a

Tenacity:

Malleable, Unctuous

Moh's Hardness:

1.0 - 2.0

Density:

2.12 - 2.15 (g/cm³)

Luminescence:

Not Fluorescent

Radioactivity:

Barely Detectable; GRapi = 128.51 (Gamma Ray American Petroleum Institute Units)  

Optical Properties

Color:

Gray, Yellowish White, White; Colorless in transmitted light

Transparency:

Transparent, Translucent, Opaque

Luster:

n/a

Refractive Index:

1.500 - 1.510  Uniaxial ( - ) 

Birefringence:

0.006 - 0.007

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

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; the most common phosphate mineral in caves.

Common Associations:

Vashegyite, Leucophosphite, Minyulite, Francoanellite, Brushite, Ardealite, Strengite, Variscite, Vivianite

Common Impurities:

None

Type Locality:

Sugar Loaf Islands, off Taranaki (now Port Taranaki), New Zealand

Year Discovered:

1865

View mineral photos:

Taranakite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

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. Gems are very, very rare (if available at all), very small, not particularily attractive and are mostly just a collector's curiosity gem. Taranakite gems are extremely rare and very small and could be considered a 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) long.

Taranakite is also noted as being the first new mineral to be discovered in New Zealand. Taranakite was first described in 1865 by James Hector, a geologist, and William Skey, a colonial New Zealand Government analyst. The material had been found by H. Richmond on the Sugar Loaf Islands of Taranaki, New Zealand. Taranakite was initially mistaken for Wavellite but was found to be a new mineral after analysis by Skey.

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". These two minerals were later identified through X-ray powder diffraction as Taranakite and discredited in favor of Taranakite by historical priority.

Distribution: 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.
 

  
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