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Pentagonite

Big Photo

Wagholi Quarry, Wagholi, Pune District (Poonah District), Maharashtra, India
© JM. Johannet

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Formula:
Ca(VO)Si
 
4
O
 
10
·4H
 
2
O
System:OrthorhombicColour:Greenish blue
Hardness:3 - 4
Name:For the pseudosymetrical five-fold habit
Dimorph of:Cavansite
This page provides mineralogical data about Pentagonite.

Classification of Pentagonite

IMA status:Approved
Strunz 8th edition ID:8/H.36-20
Nickel-Strunz 10th (pending) edition ID:9.EA.55

9 : SILICATES (Germanates)
E : Phyllosilicates
A : Single nets of tetrahedra with 4-, 5-, (6-), and 8-membered rings
Dana 8th edition ID:74.3.7.2

74 : PHYLLOSILICATES Modulated Layers
3 : Modulated Layers with joined strips
Hey's CIM Ref.:14.14.2

14 : Silicates not Containing Aluminum
14 : Silicates of V and Bi
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Type Occurrence of Pentagonite

Type Locality:Owyhee Dam, Lake Owyhee State Park, Malheur Co., Oregon, USA
Year of Discovery:1973

Occurrences of Pentagonite

Geological Setting:Fracture filling in tuffs and basalts.

Physical Properties of Pentagonite

Lustre:Vitreous
Diaphaneity (Transparency):Transparent
Colour:Greenish blue
Streak:Light blue
Hardness (Mohs):3 - 4
Tenacity:Brittle
Cleavage:Distinct/Good
Good on {010}
Density (calculated):2.33 g/cm3

Crystallography of Pentagonite

Crystal System:Orthorhombic
Class (H-M):mm2 - Pyramidal
Cell Parameters:a = 10.298(4) Å, b = 13.999(7) Å, c = 8.891(2) Å
Ratio:a:b:c = 0.736 : 1 : 0.635
Unit Cell Volume:V 1,281.74 ų (Calculated from Unit Cell)
Z:4
Morphology:Prismatic
Twinning:Cyclical by reflection accross {110}

Optical Data of Pentagonite

Type:Biaxial (-)
RI values: nα = 1.533 nβ = 1.544 nγ = 1.547
2V:Measured: 50° , Calculated: 54°
Maximum Birefringence:δ = 0.014

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Low
Dispersion:r > v strong
Pleochroism:Visible
Comments:X=Z= colorles
Y= blue

Chemical Properties of Pentagonite

Formula:
Ca(VO)Si
 
4
O
 
10
·4H
 
2
O
Essential elements:Ca, H, O, Si, V
All elements listed in formula:Ca, H, O, Si, V

Relationship of Pentagonite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
9.EA.05Cuprorivaite
CaCu[Si
 
4
O
 
10
]
9.EA.05Gillespite
BaFe
2+
 
[Si
 
4
O
 
10
]
9.EA.05Effenbergerite
BaCu[Si
 
4
O
 
10
]
9.EA.05Wesselsite
SrCu[Si
 
4
O
 
10
]
9.EA.10Ekanite
(Ca,Fe
2+
 
,Pb)
 
2
(Th,U)[Si
 
8
O
 
20
]
9.EA.15Apophyllite-(KF)
KCa
 
4
[(F,OH)|Si
 
8
O
 
20
] · 8H
 
2
O
9.EA.15Apophyllite-(KOH)
KCa
 
4
[(OH,F)|Si
 
8
O
 
20
] · 8H
 
2
O
9.EA.15Apophyllite-(NaF)
NaCa
 
4
[F|Si
 
8
O
 
20
] · 8H
 
2
O
9.EA.20Magadiite
NaSi
 
7
O
 
13
(OH)
 
3
·3H
 
2
O
9.EA.25Dalyite
K
 
2
ZrSi
 
6
O
 
15
9.EA.25Davanite
K
 
2
TiSi
 
6
O
 
15
9.EA.30Sazhinite-(Ce)
Na
 
3
Ce[Si
 
6
O
 
15
] · 6H
 
2
O
9.EA.30Sazhinite-(La)
Na
 
3
La[Si
 
6
O
 
15
] · 2H
 
2
O
9.EA.35Armstrongite
CaZr[Si
 
6
O
 
15
]·3H
 
2
O
9.EA.40Okenite
CaSi
 
2
O
 
5
·2H
 
2
O
9.EA.45Nekoite
Ca
 
3
Si
 
6
O
 
15
·7H
 
2
O
9.EA.50Cavansite
Ca(VO)Si
 
4
O
 
10
·4H
 
2
O
9.EA.60Penkvilksite
Na
 
4
Ti
 
2
Si
 
8
O
 
22
·4H
 
2
O
9.EA.60Tumchaite
Na
 
2
Zr(Si
 
4
O
 
11
)·2H
 
2
O
9.EA.65Nabesite
Na
 
2
BeSi
 
4
O
 
10
 * 4 H
 
2
O
9.EA.70Ajoite
(K,Na)Cu
 
7
[(OH)
 
6
|AlSi
 
9
O
 
24
] · 3H
 
2
O
9.EA.75Zeravshanite
Cs
 
4
Na
 
2
Zr
 
3
[Si
 
18
O
 
45
](H
 
2
O)
 
2
9.EA.80Bussyite-(Ce)
(Ce,REE)
 
3
(Na,H
 
2
O)
 
6
MnSi
 
9
Be
 
5
(O,OH)
 
30
F
 
4
Related Minerals - Hey's Index Grouping:

- +
14.14.1Cavansite
Ca(VO)Si
 
4
O
 
10
·4H
 
2
O
14.14.3Goldmanite
Ca
 
3
(V
3+
 
,Al,Fe
3+
 
)
 
2
[SiO
 
4
]
 
3
14.14.4Haradaite
SrVSi
 
2
O
 
7
14.14.5Saneroite
Na
 
2
(Mn,Mn)
 
10
Si
 
11
VO
 
34
(OH)
 
4
14.14.6Erlianite
(Fe,Mg)
 
4
(Fe,V)
 
2
Si
 
6
O
 
15
(OH,O)
 
8
14.14.7Eulytine
Bi
 
4
[SiO
 
4
]
 
3
14.14.8Bismutoferrite
Fe
3+
2
Bi[OH|(SiO
 
4
)
 
2
]

Other Names for Pentagonite

Synonyms:
IMA1971-039
Other Languages:
German:Pentagonit
Russian:Пентагонит
Spanish:Pentagonita

Other Information

Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Pentagonite

Reference List:American Mineralogist (1973): 58: 412-424.

Mineralogical Record (2003): 34: 40-43.

Internet Links for Pentagonite

Search Engines:
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    • External Links:
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  • Look for Pentagonite on Wikipedia
  • Look for Pentagonite on Mineralien Atlas
  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Pentagonite in the Natural History Museum (London) online catalogue
  • Pentagonite details from Handbook of Mineralogy (PDF)
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    Localities for Pentagonite

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    The 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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    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    India
     
    • Maharashtra
      • Pune District (Poonah District)
        • Lonavale (Lonavala)
    		Min Rec 2007 38:185-189
        • Wagholi
    		http://www.irocks.com/pentag.htm
    USA
     
    • Oregon
      • Malheur Co.
        • Lake Owyhee State Park
    		Amer.Min.(1973) 58, 405-411 and 412-424
    Mineral and/or Locality
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