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Bicapite

A valid IMA mineral species
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About BicapiteHide

Formula:
[KNa2Mg2(H2O)25][H2PV5+12O40(V5+O)2]
Colour:
dark red-brown, often appearing black
Lustre:
Vitreous
Hardness:
Specific Gravity:
2.44
Crystal System:
Tetragonal
Name:
Only known mineral with a structure based on a bicapped Keggin anion.
Structural relationship to kegginite. Unique combination of elements.

Interesting due to containing untypical vanadyl ion VO3+ with pentavalent vanadium, as opposed to the usual (for minerals) VO2+ one with tetravalent vanadium.


Unique IdentifiersHide

Mindat ID:
53141
Long-form identifier:
mindat:1:1:53141:8

IMA Classification of BicapiteHide

Classification of BicapiteHide

8.FD.10

8 : PHOSPHATES, ARSENATES, VANADATES
F : Polyphosphates, Polyarsenates, [4]-Polyvanadates
D : Polyphosphates, etc., with OH and H2O

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference for Standard
BicIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of BicapiteHide

Vitreous
Transparency:
Transparent
Colour:
dark red-brown, often appearing black
Streak:
Orange
Hardness:
1½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Very Good
{100}
Density:
2.44(2) g/cm3 (Measured)    

Optical Data of BicapiteHide

Type:
Uniaxial (+)
RI values:
nω = 1.785(5) nε = 1.81
Max. Birefringence:
δ = 0.025
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.

Surface Relief:
Moderate
Pleochroism:
Weak
Comments:
Red-brown; E > O

Chemistry of BicapiteHide

Mindat Formula:
[KNa2Mg2(H2O)25][H2PV5+12O40(V5+O)2]
Element Weights:
Element% weight
O53.539 %
V35.620 %
H2.618 %
Mg2.428 %
Na2.296 %
K1.953 %
P1.547 %

Calculated from ideal end-member formula.

Crystallography of BicapiteHide

Crystal System:
Tetragonal
Class (H-M):
4/m - Dipyramidal
Space Group:
I4/m
Cell Parameters:
a = 11.545(1) Å, c = 20.546(1) Å
Ratio:
a:c = 1 : 1.78
Unit Cell V:
2738.3 ų
Z:
2

X-Ray Powder DiffractionHide

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 7: Great Oxidation Event<2.4
47e : [Vanadates, chromates, manganates]
Stage 10b: Anthropogenic minerals<10 Ka
55 : Anthropogenic mine minerals

Type Occurrence of BicapiteHide

General Appearance of Type Material:
square tablets up to about 0.2 mm on edge
Place of Conservation of Type Material:
Cotypes: the mineralogical collections of the Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA 90007, USA, catalogue numbers 66915 and 66916
Associated Minerals at Type Locality:

Synonyms of BicapiteHide

Other Language Names for BicapiteHide

Dutch:Bicapiet
German:Bicapit

Common AssociatesHide

Associations Based on Photo Data:
1 photo of Bicapite associated with HuemuliteNa4Mg(V10O28) · 24H2O
1 photo of Bicapite associated with GypsumCaSO4 · 2H2O

Related Minerals - Strunz-mindat GroupingHide

8.FD.05VolborthiteCu3(V2O7)(OH)2 · 2H2OMon. 2/m : B2/m
8.FD.05MartyiteZn3(V2O7)(OH)2 · 2H2OTrig. 3m : P3m1
8.FD.05KarpenkoiteCo3(V2O7)(OH)2 · 2H2OTrig. 3m (3 2/m) : P3m1
8.FD.10VanarsiteNaCa12(As3+V5+8.5V4+3.5As5+6O51)2 · 78H2OMon. 2/m : P21/b
8.FD.10PackratiteCa11(As3+V5+10V4+2As5+6O51)2 · 83H2OTric. 1 : P1
8.FD.10MorrisoniteCa11(As3+V4+2V5+10As5+6O51)2 · 78H2OMon. 2/m : P21/b
8.FD.10LumsdeniteNaCa3Mg2(As3+V4+2V5+10As5+6O51) · 45H2OTric. 1 : P1
8.FD.10GatewayiteCa6(As3+V4+3 V5+9As5+6O51) · 31H2OMon. 2 : P21
8.FD.10KegginitePb3Ca3[AsV12O40(VO)] · 20H2OTrig. 3 : P3
8.FD.15ChinchorroiteNa2Mg5(As2O7)2(AsO3OH)2(H2O)10Tric. 1 : P1

RadioactivityHide

Radioactivity:
Element % Content Activity (Bq/kg) Radiation Type
Uranium (U) 0.0000% 0 α, β, γ
Thorium (Th) 0.0000% 0 α, β, γ
Potassium (K) 1.9528% 605 β, γ

For comparison:

  • Banana: ~15 Bq per fruit
  • Granite: 1,000–3,000 Bq/kg
  • EU exemption limit: 10,000 Bq/kg

Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.

Interactive Simulator:

Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!

Activity:

DistanceDose rateRisk
1 cm
10 cm
1 m

The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).

D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield

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.

Internet Links for BicapiteHide

References for BicapiteHide

Localities for BicapiteHide

Showing 1 localities.

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.
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Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for references and 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 (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
USA (TL)
 
  • Colorado
    • Montrose County
Hålenius et al. (2018) +1 other reference
 
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