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Greifensteinite
A valid IMA mineral species
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About Greifensteinite
Formula:
Ca2Fe2+5Be4(PO4)6(OH)4 · 6H2O
Colour:
Dark olive-green
Lustre:
Vitreous
Hardness:
4½
Specific Gravity:
2.93
Crystal System:
Monoclinic
Member of:
Name:
For the type locality, at the Greifenstein Rocks, Ehrenfriedersdorf, Erzgebirge, Saxony, Germany.
Dimorph of:
Isostructural with:
Unique Identifiers
Mindat ID:
11356
Long-form identifier:
mindat:1:1:11356:8
IMA Classification of Greifensteinite
Approved
IMA Formula:
Ca2Fe2+5Be4(PO4)6(OH)4·6H2O
Approval year:
2001
First published:
2002
Classification of Greifensteinite
8.DA.10
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
A : With small (and occasionally larger) cations
8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
A : With small (and occasionally larger) cations
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Gfs | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Greifensteinite
Vitreous
Transparency:
Transparent, Translucent
Colour:
Dark olive-green
Streak:
White
Hardness:
4½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
Good on {100}
Good on {100}
Fracture:
Irregular/Uneven
Density:
2.93(2) g/cm3 (Measured) 2.95 g/cm3 (Calculated)
Optical Data of Greifensteinite
Type:
Biaxial (-)
RI values:
nα = 1.624(2) nβ = 1.634(2) nγ = 1.638(2)
2V:
Measured: 80° , Calculated: 64°
Max. Birefringence:
δ = 0.014
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Pleochroism:
Visible
Comments:
X = light bluish green, Y = light green, Z = brownish green
Comments:
X = b
Greifensteine, Ehrenfriedersdorf, Erzgebirgskreis, Saxony, Germany