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⇱ Bettertonite: Mineral information, data and localities.

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Bettertonite

A valid IMA mineral species
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About BettertoniteHide

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Formula:
[Al6(AsO4)3(OH)9(H2O)5] · 11H2O
Colour:
White
Lustre:
Vitreous, Silky, Pearly
Specific Gravity:
2.02 (Calculated)
Crystal System:
Monoclinic
Name:
Honors John Betterton (b. 1959, London), a museum geologist/mineralogist at Haslemere Educational Museum, Surrey, England, for his extensive contributions to the characterisation of minerals from the Penberthy Croft mine for more than 30 years. Also is an advanced mineral collector and micromounter.
New structure type, closely related to that of penberthycroftite; both structures are flexible layered type, comprising corner-linked columns of heteropolyhedra.

Chemically similar to liskeardite.

Transforms to penberthycroftyite at relatively low temperatures (see Thermal Behaviour section).


Unique IdentifiersHide

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Mindat ID:
46516
Long-form identifier:
mindat:1:1:46516:0

IMA Classification of BettertoniteHide

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Approved
IMA Formula:
Al6(AsO4)3(OH)9(H2O)5 · 11H2O
Approval year:
2014
First published:
2015

Classification of BettertoniteHide

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8.DD.

8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
D : With only medium-sized cations, (OH, etc.):RO4= 2:1

Mineral SymbolsHide

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

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

Pronunciation of BettertoniteHide

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Pronunciation:
PlayRecorded byCountry
Jolyon RalphUnited Kingdom

Physical Properties of BettertoniteHide

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Vitreous, Silky, Pearly
Transparency:
Translucent
Comment:
Vitreous to pearly, somewhat silky lustre
Colour:
White
Streak:
White
Tenacity:
Flexible
Fracture:
Irregular/Uneven
Density:
2.02 g/cm3 (Calculated)

Optical Data of BettertoniteHide

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Type:
Biaxial (+)
RI values:
nα = 1.511(1) nβ = 1.517(1) nγ = 1.523(1)
Max. Birefringence:
δ = 0.012
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
Optical Extinction:
X = c; Y = b; Z = a.
Pleochroism:
Non-pleochroic

Chemistry of BettertoniteHide

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Mindat Formula:
[Al6(AsO4)3(OH)9(H2O)5] · 11H2O
Element Weights:
Element% weight
O58.040 %
As22.037 %
Al15.872 %
H4.052 %

Calculated from ideal end-member formula.

Crystallography of BettertoniteHide

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Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/c
Cell Parameters:
a = 7.773(2) Å, b = 26.991(5) Å, c = 15.867(3) Å
β = 94.22(3)°
Ratio:
a:b:c = 0.288 : 1 : 0.588
Unit Cell V:
3,319.89 ų (Calculated from Unit Cell)
Morphology:
Ultrathin rectangular laths, with lateral dimensions generally <20 μm. The laths are flattened on {010} and exhibit the forms {010}, {100} and {001}.

X-Ray Powder DiffractionHide

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Powder Diffraction Data:
d-spacingIntensity
13.648 Å(100)
13.505 Å(50)
7.805 Å(50)
7.461 Å(30)
5.880 Å(20)
5.622 Å(12)
3.589 Å(20)
2.857 Å(14)
Comments:
From Type Description.

Geological EnvironmentHide

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Paragenetic Mode(s):

Type Occurrence of BettertoniteHide

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General Appearance of Type Material:
As tufts of white, ultrathin (sub-micrometre) rectangular laths, with lateral dimensions generally <20 μm.
Place of Conservation of Type Material:
Cotype material is deposited in the mineralogical collections of Museum Victoria, Melbourne, Victoria, Australia, registration number M53274, and the Natural History Museum, London, UK, registration number BM2014,100
Associated Minerals at Type Locality:

Synonyms of BettertoniteHide

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Other Language Names for BettertoniteHide

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Common AssociatesHide

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Associations Based on Photo Data:
5 photos of Bettertonite associated with QuartzSiO2
3 photos of Bettertonite associated with ChamositeFe2+5Al(AlSi3O)10(OH)8
2 photos of Bettertonite associated with ArsenopyriteFeAsS
1 photo of Bettertonite associated with GoethiteFe3+O(OH)
1 photo of Bettertonite associated with PharmacosideriteKFe3+4(AsO4)3(OH)4 · 6-7H2O

Related Minerals - Strunz-mindat GroupingHide

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8.DD.Penberthycroftite[Al6(AsO4)3(OH)9(H2O)5] · 8H2OMon. 2/m : P21/b
8.DD.VargiteMnCu2Mn2(AsO4)2(OH)4(H2O)4Mon. 2/m : P21/b
8.DD.GaleaclolusiteAl6(AsO4)3(OH)9(H2O)4 · 8H2OOrth. mmm(2/m2/m2/m) : Pnma
8.DD.05LuetheiteCu2Al2(AsO4)2(OH)4Mon. 2/m : P21/m
8.DD.05ChenevixiteCu2Fe3+2(AsO4)2(OH)4Mon. 2/m : P21/m
8.DD.10AkrochorditeMnMn2Mn2(AsO4)2(OH)4(H2O)4Mon. 2/m : P21/b
8.DD.10GuanacoiteMgCu2Mg2(AsO4)2(OH)4(H2O)4Mon. 2/m : P21/b
8.DD.15'UM1981-32-PO:FeH'Fe2+Fe3+6(PO4)4-x[PO3(OH)]x(OH)8 · 4H2O
8.DD.15AfmiteAl3(OH)4(H2O)3(PO4)(PO3OH) · H2OTric. 1 : P1
8.DD.15Aheylite(Fe2+,Zn)Al6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15'Coeruleolactite'Tric. 1 : P1
8.DD.15FaustiteZnAl6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15PlaneriteAl6(PO4)2(PO3OH)2(OH)8 · 4H2OTric. 1 : P1
8.DD.15ChalcosideriteCuFe3+6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15TurquoiseCuAl6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.20EosphoriteMn2+Al(PO4)(OH)2 · H2OOrth. mmm(2/m2/m2/m) : Cmca
8.DD.20Ernstite(Mn2+,Fe3+)Al(PO4)(OH,O)2 · H2OMon.
8.DD.20LefontiteFe2Al2Be(PO4)2(OH)6Orth. mmm(2/m2/m2/m) : Cmca
8.DD.20ChildreniteFe2+Al(PO4)(OH)2 · H2OOrth. mm2 : Ccc2
8.DD.25KobokoboiteAl6(PO4)4(OH)6 · 11H2O Tric.
8.DD.30SmamiteCa2Sb(OH)4[H(AsO4)2] · 6H2OTric. 1 : P1
8.DD.35'Gutsevichite'Al3(PO4)2(OH)3 · 8H2OIso.
8.DD.40'Laubmannite (of Moore)'(Fe3+,Fe2+,M)8+x(OH,H2O)9(H2O)2(PO4)5, M = Fe3+, Cu2+ or other metal cation, x ~ 0.1.Orth. mmm(2/m2/m2/m) : Pbcm

Other InformationHide

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Thermal Behaviour:
Transformation to penberthycroftyite: 67-97°C, associated with 8% contraction of layer separation and 6Å relative sliding of the adjacent layers; T>100°C: formation of a "displaced-layer" phase, associated with further 8% layer contraction.
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 BettertoniteHide

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mindat.org URL:
https://www.mindat.org/min-46516.html
Please feel free to link to this page.

References for BettertoniteHide

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Reference List:

Localities for BettertoniteHide

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Showing 1 localities.

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

Locality ListHide

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👁 Image
- This locality has map coordinates listed. 👁 Image
- This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. 👁 Image
- Good crystals or important locality for species. 👁 Image
- 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.
UK (TL)
  • England
    • Cornwall
      • St Hilary
Williams et al. (2015) +1 other reference
Quick NavTopAbout BettertoniteUnique IdentifiersIMA Classification Classification Mineral SymbolsPronunciation Physical Properties Optical Data Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
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To cite: Ralph, J., Von Bargen, D., Martynov, P., Zhang, J., Que, X., Prabhu, A., Morrison, S. M., Li, W., Chen, W., & Ma, X. (2025). Mindat.org: The open access mineralogy database to accelerate data-intensive geoscience research. American Mineralogist, 110(6), 833–844. doi:10.2138/am-2024-9486.
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