May 8 2013
Taranakite is a hydrated alkali iron-aluminium phosphate mineral. The mineral was named after the place it was first discovered- Taranaki Peninsula, New Zealand.
Properties of Taranakite
The following are the key properties of taranakite:
- Cell Data
- Space group: R3c (synthetic)
- a = 8.7025(11)
- c = 95.05(1)
- Z = 6
- Crystal Data
- Hexagonal
- Point group: 3 2/m
- Pseudohexagonal platy crystals- rarely to 0.5 mm and typically in compact nodular aggregates, pulverulent, powdery, flourlike to claylike massive
- X-ray powder pattern: 15.82 (100), 3.82 (40), 3.14 (31), 3.36 (29), 7.47 (28), 3.59 (22), 7.92 (18)
- Chemical Composition
| Elements |
Content 1 |
Content 2 |
Content 3 |
| P2O5 |
42.32 |
41.88 |
42.30 |
| H2O |
31.10 |
28.43 |
28.18 |
| Al2O3 |
19.03 |
17.48 |
18.99 |
| K2O |
7.09 |
8.43 |
10.53 |
| Fe2O3 |
0.42 |
1.67 |
- |
| Na2O |
- |
1.28 |
- |
| Insol. |
- |
0.37 |
- |
| Total |
99.96 |
99.54 |
100.00 |
- Optical Properties
- Optical Class: Uniaxial (–)
- ω = 1.506–1.510
- ε = 1.500–1.503
- Estimated Properties
| Electron density |
Bulk density (electron density)= 2.19 g/cm3
note: Specific gravity of taranakite = 2.15 g/cm3 |
| Photoelectric |
PETaranakite = 2.09 barns/electron
U=PETaranakite x ρelectron density= 4.58 barns/cm3 |
| Fermion index |
Fermion index = 0.000301283
Boson index = 0.999698717 |
Radioactivity
|
GRapi = 128.51 (Gamma Ray American Petroleum Institute Units)
Taranakite is radioactive (barely detectable) |
How to Identify Taranakite
Taranakite can be identified in the field by its gray white, yellowish white, or white color variations. The appearance of this mineral is transparent. It is a non-fluorescent mineral with a white streak. The density of taranakite is 2.09 g/cm3 and hardness is 1-2 - between talc and gypsum.
Global Distribution
Taranakite is widely distributed in the following locations:
- New Zealand - From the Sugarloaves, near New Plymouth, Taranaki Peninsula
- Argentina - Island Leones, Patagonia
- On R´eunion Island, Indian Ocean
- King George Island, Maritime Antarctic
- Australia - in the Russenden Cave, Queensland; the Skipton lava tube caves, southwest of Ballarat, Victoria; in caves at Mimegarra, Western Australia; and the Jenolan Caves, New South Wales
- Malaysia - From the Niah Great Cave, Sarawak
- Japan - In the Onino-Iwaya Cave, Hiroshima Prefecture
- South Africa - In Etienne’s Cave, and well-crystallized in Christmas Cave, Transvaal Bulgaria - From the Bacho Kuo Cave
- China - In the Yangsue Posayen Cave, 20 km south of Guilin, Guangxi Province
- France - In the Minerva Grotto, Fauzan, H´erault
- Algeria - From the Tour Combes Cave, near Oran
- USA - in the Pig Hole Cave, Giles Co., Virginia; and the Low Water Bridge Cave, Greene Co., Missouri
- Italy - in the Castellana Cave, south of Bari, Puglia; on Monte Alburno, near Controne, Salerno.
Occurrence of Taranakite and Useful Mineral Association
Taranakite is often associated with minerals such as ardealite, vashegyiteminyulite, francoanellite, leucophosphite, brushite, strengite, variscite, and vivianite. Taranakite is formed from phosphatic solutions derived from bird or bat guano reacting with clays or aluminous rocks under perenially damp conditions. It is the most common phosphate mineral found in caves.
References