Arnhemite

Cave Name:

Arnhem Cave, Namibia - mineral species not approved by IMA

First description of cave occurrence:

Martini, J. E. 1994. Two new minerals originated from bat guano combustion in Arnhem Cave, Namibia. Bulletin of the South African Speleological Association 33: 66-69

First description of non-cave occurrence:

Other cave locations & References:

Hibashi Cave. Saudi Arabia - Pint, J.J., Al-Shanti, M.A., Al-Juaid, A.J., Al-Amoudi, S.A. & Forti, P. 2005. Ghar al Hibashi Harrat Nawasif/Al Buqum, Kingdom of Saudi Arabia. Saudi Geological Survey Open-File Report SGS-OF-2004-12: 68pp (http://www.i-pi.com/~ingham/saudicaves/hib-4-12.pdf)

Latitude: 22°42'5''S

Longitude: 18°5'47''E

Length: 4500

Water: No

Type of rock:

Age: Precambrian

Cave temperature (°C): 25

Group: Phosphates

Chemical formula:
[According to the official IMA-CNMNC List of Mineral Names (http://nrmima.nrm.se/imalist.htm)]

K₄Mg₂(P₂O₇)·5H₂O

Deposition and stability:

It is not a a direct product of guano combustion, but is the likely formed by secondary hydration of a primary anhydrous K-Mg pyrophosphate generated at high temperature. No relic of such a pyrophosphate has been identified in the white slag.

Habit: Powdery (very fine grained)

Color: White

Luster: Pearly

Hardness: Low (not measured)

Cleavage: Extinction if parallel to the cleavage {001}

Identified by:

Cell parameter a (Å): 11.06

Cell parameter c (Å): 16.75

Crystal size: 1 to 50 microns

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