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⇱ Penberthycroftite: Mineral information, data and localities.

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Penberthycroftite

A valid IMA mineral species
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About PenberthycroftiteHide

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Formula:
[Al6(AsO4)3(OH)9(H2O)5] · 8H2O
Colour:
White
Lustre:
Vitreous, Pearly
Specific Gravity:
2.18 (Calculated)
Crystal System:
Monoclinic
Name:
The mineral is named for the location where the mineral was found, Penberthy Croft mine.
Closely related to bettertonite, which is a higher hydrate. Also chemically similar to liskeardite, bulachite, and hydroniumpharmacoalumite; and to mansfieldite.

The structure is heteropolyhedral layered one, with undulating layering || {010}. In the structure there are channels along [100] holding water molecules. The layers are identical to that in bettertonite, but are mutually displaced along [001] and [010] resulting in the interlayer volume decrease, by ca. 10%, when compared to bettertonite.


Unique IdentifiersHide

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Mindat ID:
46688
Long-form identifier:
mindat:1:1:46688:6

IMA Classification of PenberthycroftiteHide

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Approved
Approval year:
2015
First published:
2016

Classification of PenberthycroftiteHide

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

Pronunciation of PenberthycroftiteHide

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Pronunciation:
PlayRecorded byCountry
Jolyon RalphUnited Kingdom

Physical Properties of PenberthycroftiteHide

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Vitreous, Pearly
Transparency:
Translucent
Comment:
Crusts have dull and nearly waxy lustre.
Colour:
White
Streak:
White
Tenacity:
Flexible
Cleavage:
Perfect
Basal cleavage on {010}
Density:
2.18 g/cm3 (Calculated)

Chemistry of PenberthycroftiteHide

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Mindat Formula:
[Al6(AsO4)3(OH)9(H2O)5] · 8H2O
Element Weights:
Element% weight
O56.318 %
As23.270 %
Al16.760 %
H3.652 %

Calculated from ideal end-member formula.
Common Impurities:
S,(Fe)

Crystallography of PenberthycroftiteHide

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Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/c
Cell Parameters:
a = 7.753(2) Å, b = 24.679(5) Å, c = 15.679(3) Å
β = 94.19(3)°
Ratio:
a:b:c = 0.314 : 1 : 0.635
Unit Cell V:
2,991.94 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Tufts and sprays of ultrathin (sub-micrometre) rectangular or bladelike laths, with lateral dimensions generally less than 20µm.

X-Ray Powder DiffractionHide

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Powder Diffraction Data:
d-spacingIntensity
13.264 Å(46)
12.402 Å(16)
9.732 Å(100)
7.420 Å(28)
5.670 Å(8)
5.423 Å(6)
3.598 Å(6)
3.562 Å(6)

Geological EnvironmentHide

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Paragenetic Mode(s):

Type Occurrence of PenberthycroftiteHide

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General Appearance of Type Material:
Dense lath-like crystal aggregates within a matrix of quartz, chamosite and arsenopyrite.
Place of Conservation of Type Material:
Co-type material is deposited in the mineralogical collections of the Natural History Museum, London, Registration number BM.2015.3 and the Museum Victoria, Australia, registration number M53452
Geological Setting of Type Material:
The arsenate mineral assemblage at Penberthy Croft is interpreted as having formed from prolonged oxidation of various sulphides in the upper parts of lodes and veins within the mine and on dump material.
Associated Minerals at Type Locality:

Synonyms of PenberthycroftiteHide

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Other Language Names for PenberthycroftiteHide

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Common AssociatesHide

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Associated Minerals Based on Photo Data:
1 photo of Penberthycroftite associated with PharmacosideriteKFe3+4(AsO4)3(OH)4 · 6-7H2O

Related Minerals - Strunz-mindat GroupingHide

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8.DD.Bettertonite[Al6(AsO4)3(OH)9(H2O)5] · 11H2OMon. 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.15UM1981-32-PO:FeHFe2+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.15CoeruleolactiteTric. 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.35GutsevichiteAl3(PO4)2(OH)3 · 8H2OIso.
8.DD.40Laubmannite (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

Fluorescence of PenberthycroftiteHide

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Other InformationHide

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Thermal Behaviour:
Two endotherms corresponding to water evolution were recorded at 94 and 180°C, and an endotherm due to SO3 evolution occurred at 481°C; will from from bettertonite at 67-97oC, the process being associated with 8% contraction of laye
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 PenberthycroftiteHide

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mindat.org URL:
https://www.mindat.org/min-46688.html
Please feel free to link to this page.

References for PenberthycroftiteHide

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Reference List:

Localities for PenberthycroftiteHide

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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
Hålenius et al. (2015) +1 other reference
Quick NavTopAbout PenberthycroftiteUnique IdentifiersIMA Classification Classification Mineral SymbolsPronunciation Physical Properties Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatFluorescence Other InformationInternet Links References Localities Locality List
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