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Pentagonite

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Formula:
Ca(VO)Si4O10 · 4H2O
Colour:
Greenish blue
Lustre:
Vitreous
Hardness:
3 - 4
Specific Gravity:
2.33 (Calculated)
Crystal System:
Orthorhombic
Name:
For the pseudosymmetrical five-fold habit of the typical pentagonite twins.
Dimorph of:
Structurally related to plumbophyllite.

Ishida et al. (2009) suggest that cavansite is a low-temperature form and pentagonite a high-temperature form.


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Classification of PentagoniteHide

Approved
9.EA.55

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

74 : PHYLLOSILICATES Modulated Layers
3 : Modulated Layers with joined strips
14.14.2

14 : Silicates not Containing Aluminum
14 : Silicates of V and Bi

Physical Properties of PentagoniteHide

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

Optical Data of PentagoniteHide

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

Chemical Properties of PentagoniteHide

Formula:
Ca(VO)Si4O10 · 4H2O
IMA Formula:
CaV4+OSi4O10 · 4H2O

Crystallography of PentagoniteHide

Crystal System:
Orthorhombic
Class (H-M):
mm2 - Pyramidal
Cell Parameters:
a = 10.386(4) Å, b = 14.046(7) Å, c = 8.975(2) Å
Ratio:
a:b:c = 0.739 : 1 : 0.639
Unit Cell V:
1,309.29 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Prismatic, bladed.
Twinning:
Cyclical by reflection across {110}.
Comment:
Space group Ccm21.

Type Occurrence of PentagoniteHide

Synonyms of PentagoniteHide

Other Language Names for PentagoniteHide

Common AssociatesHide

Associated Minerals Based on Photo Data:
Calcite61 photos of Pentagonite associated with Calcite on mindat.org.
Mordenite50 photos of Pentagonite associated with Mordenite on mindat.org.
Stilbite-Ca42 photos of Pentagonite associated with Stilbite-Ca on mindat.org.
Stilbite37 photos of Pentagonite associated with Stilbite on mindat.org.
Heulandite23 photos of Pentagonite associated with Heulandite on mindat.org.
Cavansite7 photos of Pentagonite associated with Cavansite on mindat.org.
Gyrolite5 photos of Pentagonite associated with Gyrolite on mindat.org.
Quartz4 photos of Pentagonite associated with Quartz on mindat.org.
Heulandite-Ca3 photos of Pentagonite associated with Heulandite-Ca on mindat.org.
Cleavelandite3 photos of Pentagonite associated with Cleavelandite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

9.EA.05CuprorivaiteCaCuSi4O10Tet. 4/mmm (4/m 2/m 2/m) : P4/ncc
9.EA.05GillespiteBaFe2+Si4O10Tet.
9.EA.05EffenbergeriteBaCuSi4O10Tet. 4/mmm (4/m 2/m 2/m) : P4/ncc
9.EA.05WesselsiteSrCuSi4O10Tet.
9.EA.10EkaniteCa2ThSi8O20Tet. 4 2 2 : I4 2 2
9.EA.15Fluorapophyllite-(K)KCa4(Si8O20)(F,OH) · 8H2OTet. 4/mmm (4/m 2/m 2/m) : P4/mnc
9.EA.15Hydroxyapophyllite-(K)KCa4(Si8O20)(OH,F) · 8H2OTet.
9.EA.15Fluorapophyllite-(Na)NaCa4(Si8O20)F · 8H2OOrth.
9.EA.20MagadiiteNa2Si14O29 · 11H2OMon.
9.EA.25DalyiteK2ZrSi6O15Tric.
9.EA.25DavaniteK2TiSi6O15Tric.
9.EA.30Sazhinite-(Ce)Na2CeSi6O14•6H2O
9.EA.30Sazhinite-(La)Na3La[Si6O15] · 2H2OOrth. mm2 : Pmm2
9.EA.35ArmstrongiteCaZr[Si6O15] · 3H2OMon.
9.EA.40OkeniteCa10Si18O46 · 18H2OTric. 1 : P1
9.EA.45NekoiteCa3Si6O15·7H2OTric. 1 : P1
9.EA.50CavansiteCa(VO)Si4O10 · 4H2OOrth. mmm (2/m 2/m 2/m)
9.EA.60PenkvilksiteNa4Ti2Si8O22 · 4H2OOrth. mmm (2/m 2/m 2/m) : Pbcn
9.EA.60TumchaiteNa2Zr(Si4O11) · 2H2OMon.
9.EA.65NabesiteNa2BeSi4O10 · 4H2OOrth. 2 2 2 : P21 21 21
9.EA.70Ajoite(K,Na)Cu7AlSi9O24(OH)6 · 3H2OTric.
9.EA.75ZeravshaniteNa2Cs4Zr3[Si18O45]*2H2OMon. 2/m : B2/b
9.EA.80Bussyite-(Ce)(Ce,REE)3(Na,H2O)6MnSi9Be5(O,OH)30F4Mon. 2/m : B2/b
9.EA.85PlumbophyllitePb2Si4O10 · H2OOrth. mmm (2/m 2/m 2/m) : Pbcn

Related Minerals - Dana Grouping (8th Ed.)Hide

74.3.7.1CavansiteCa(VO)Si4O10 · 4H2OOrth. mmm (2/m 2/m 2/m)

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

14.14.1CavansiteCa(VO)Si4O10 · 4H2OOrth. mmm (2/m 2/m 2/m)
14.14.3GoldmaniteCa3V3+2(SiO4)3Iso.
14.14.4HaradaiteSrVSi2O7Orth.
14.14.5SaneroiteNaMn2+5[Si5O14(OH)](VO3)(OH)Tric.
14.14.6Erlianite(Fe,Mg)4(Fe,V)2Si6O15(OH,O)8Orth.
14.14.7EulytineBi4(SiO4)3Iso. 4 3m : I4 3d
14.14.8BismutoferriteFe3+2Bi(SiO4)2(OH)Mon. m : Bm

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.

References for PentagoniteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Staples, L.W., H.T. Evans, Jr., and J.R. Lindsay (1973): Cavansite and pentagonite, new dimorphous calcium vanadium silicate minerals from Oregon. Amer. Mineral., 58, 405-411.
Evans, H.T., Jr. (1973): The crystal structures of cavansite and pentagonite. Amer. Mineral., 58, 412-424.
Mineralogical Record (2003): 34: 40-43.
Ishida, N., Kimata, M., Nishida, N., Hatta, T., Shimizu, M., Akasaka, T. (2009): Polymorphic relation between cavansite and pentagonite: Genetic implications of oxonium ion in cavansite. Journal of Mineralogical and Petrological Sciences, 104, 241-252.
Danisi, R. M. , Armbruster, T., and Lazic, B. (2012): In situ dehydration behavior of zeolite-like pentagonite: A single-crystal X-ray study. Journal of Solid State Chemistry 197, 508-516.

Internet Links for PentagoniteHide

Localities for PentagoniteHide

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.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for 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 (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
India
 
  • Maharashtra
    • Pune District (Poonah District)
      • Lonavale (Lonavala)
Praszkier, T. & Siuda, R. (2007): The Lonavala Quarry, Pune District, Maharashtra, India. Mineralogical Record 38: 185-189
      • Talegaon
Praszkier, T. (2009): Cavansit und Pentagonit aus Indien. Mineralien-Welt 20 (6), 16-25.
Praszkier, T. (2009): Cavansit und Pentagonit aus Indien. Mineralien-Welt 20 (6), 16-25.
http://www.irocks.com/pentag.htm
USA (TL)
 
  • Oregon
    • Malheur Co.
      • Lake Owyhee State Park
Amer.Min.(1973) 58, 405-411 and 412-424
Mineral and/or Locality  
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