Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat Articles
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsThe ElementsUsersBooks & MagazinesMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery


This page is currently not sponsored. Click here to sponsor this page.
(K,Na)4Mg2(P2O7)2 · 5H2O
Crystal System:
Named after its locality.
A hydrated pyrophospate originated from hydration of slag formed by bat guano combustion in Arnhem Cave, Namibia, about 2000 years ago. Cause of combustion unknown.
See also pyrocoproite and pyrophosphite.

Originally reported from Arnhem Cave, Windhoek District, Khomas Region, Namibia.

Hide all sections | Show all sections

Classification of ArnhemiteHide

Unnamed (probably valid)
Approval History:
Unnamed, but probably valid.

F : Polyphosphates, Polyarsenates, [4]-Polyvanadates
C : Polyphosphates, etc., with H2O only

Physical Properties of ArnhemiteHide


Optical Data of ArnhemiteHide

Uniaxial (-)
RI values:
nω = 1.516 nε = 1.503
Max Birefringence:
δ = 0.013
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:

Chemical Properties of ArnhemiteHide

(K,Na)4Mg2(P2O7)2 · 5H2O

Crystallography of ArnhemiteHide

Crystal System:

Other Language Names for ArnhemiteHide


Related Minerals - Nickel-Strunz GroupingHide

8.FC.05FianeliteMn2+2((V,As)2O7) · 2H2OMon.
8.FC.10CanaphiteNa2Ca(P2O7) · 4H2OMon.
8.FC.15PintadoiteCa2(V2O7) · 9H2O
8.FC.25WooldridgeiteNa2CaCu2+2(P2O7)2 · 10H2OOrth. mm2 : Fdd2
8.FC.30KanoneroviteNa3Mn2+(P3O10) · 12H2OMon. 2/m

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for ArnhemiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Martini, J. E. J. (1994): Two new minerals originated from bat guano combustion in Arnhem Cave, Namibia. South African Speleological Assoc. Bull. 33, 66-69. [Abstract in Am. Mineral. 84, 193]

Internet Links for ArnhemiteHide

Localities for ArnhemiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
  • Khomas Region
    • Windhoek District
[South African Speleological Assoc.(1994) 33, 66-69; AmMin 84:193]
Saudi Arabia
  • Mintaqah Makkah
Saudi Geological Survey Open-File Report SGS-OF-2004-12, 68 p.
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2019, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: April 19, 2019 01:26:41 Page generated: March 23, 2019 14:29:27
Go to top of page