Arnhemite and pyrophosphite are the principal phases in a slag that forms a thin layer in a profile of cave soil. The slag is interpreted to have resulted from the melting of ashes during the combustion of bat quano.
IMA Status:
Not Approved IMA
Locality:
Arhem Cave, 150 km east of Windhoek, Namibia. Link to MinDat.org Location Data.
Name Origin:
Named after the Greek pyros, meaning fire and the element name - Phosphorus.
Pyrophosphite Crystallography
Axial Ratios:
a:b:c =1.7233:1:2.2917
Cell Dimensions:
a = 9.742, b = 5.653, c = 12.955, Z = 4; beta = 104.35° V = 691.19 Den(Calc)= 2.76
Friable - The crumbly disintegration of earthy materials or highly fractured minerals.
Habit:
Anhedral Grains - Granular minerals without the expression of crystal shapes
Habit:
Microscopic Crystals - Crystals visible only with microscopes.
Luster:
Vitreous (Glassy)
Streak:
white
Optical Properties of Pyrophosphite
Gladstone-Dale:
CI meas= -0.031 (Excellent) - where the CI = (1-KPDmeas/KC) CI calc= -0.029 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1978,KPDmeas= 0.1982,KC= 0.1922 Ncalc = 1.53
Optical Data:
Biaxial (?), a=1.543, g=1.549, bire=0.0060
Calculated Properties of Pyrophosphite
Electron Density:
Bulk Density (Electron Density)=2.72 gm/cc note: Specific Gravity of Pyrophosphite =2.76 gm/cc.
Fermion Index:
Fermion Index = 0.0009101723 Boson Index = 0.9990898277
Photoelectric:
PEPyrophosphite = 5.20 barns/electron U=PEPyrophosphite x relectron= 14.15 barns/cc.
Radioactivity:
GRapi = 346.36 (Gamma Ray American Petroleum Institute Units)
Concentration of Pyrophosphite per GRapi unit = 0.29 (%)
Estimated Radioactivity from Pyrophosphite - barely detectable
Chemical Formula: 
- barely detectable