Pentagonite
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About Pentagonite
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.
Ishida et al. (2009) suggest that cavansite is a low-temperature form and pentagonite a high-temperature form.
Classification of Pentagonite
Approved
8/H.36-20
9.EA.55
9 : SILICATES (Germanates)
E : Phyllosilicates
A : Single nets of tetrahedra with 4-, 5-, (6-), and 8-membered rings
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
74 : PHYLLOSILICATES Modulated Layers
3 : Modulated Layers with joined strips
14.14.2
14 : Silicates not Containing Aluminum
14 : Silicates of V and Bi
14 : Silicates not Containing Aluminum
14 : Silicates of V and Bi
Physical Properties of Pentagonite
Vitreous
Transparency:
Transparent
Colour:
Greenish blue
Streak:
Light blue
Hardness:
3 - 4 on Mohs scale
Tenacity:
Brittle
Cleavage:
Distinct/Good
Good on {010}
Good on {010}
Density:
2.33 g/cm3 (Calculated)
Optical Data of Pentagonite
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.
and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
r > v strong
Pleochroism:
Visible
Comments:
X=Z= colourless
Y= blue
Y= blue
Chemical Properties of Pentagonite
Formula:
Ca(VO)Si4O10 · 4H2O
IMA Formula:
CaV4+OSi4O10 · 4H2O
Crystallography of Pentagonite
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 Pentagonite
Synonyms of Pentagonite
Other Language Names for Pentagonite
Common Associates
Associated Minerals Based on Photo Data:
| Calcite | 61 photos of Pentagonite associated with Calcite on mindat.org. |
| Mordenite | 50 photos of Pentagonite associated with Mordenite on mindat.org. |
| Stilbite-Ca | 42 photos of Pentagonite associated with Stilbite-Ca on mindat.org. |
| Stilbite subgroup | 37 photos of Pentagonite associated with Stilbite subgroup on mindat.org. |
| Heulandite subgroup | 23 photos of Pentagonite associated with Heulandite subgroup on mindat.org. |
| Cavansite | 7 photos of Pentagonite associated with Cavansite on mindat.org. |
| Gyrolite | 5 photos of Pentagonite associated with Gyrolite on mindat.org. |
| Quartz | 4 photos of Pentagonite associated with Quartz on mindat.org. |
| Heulandite-Ca | 3 photos of Pentagonite associated with Heulandite-Ca on mindat.org. |
| Cleavelandite | 3 photos of Pentagonite associated with Cleavelandite on mindat.org. |
Related Minerals - Nickel-Strunz Grouping
| 9.EA.05 | Cuprorivaite | CaCuSi4O10 | Tet. 4/mmm (4/m 2/m 2/m) : P4/ncc |
| 9.EA.05 | Gillespite | BaFe2+Si4O10 | Tet. |
| 9.EA.05 | Effenbergerite | BaCuSi4O10 | Tet. 4/mmm (4/m 2/m 2/m) : P4/ncc |
| 9.EA.05 | Wesselsite | SrCuSi4O10 | Tet. |
| 9.EA.10 | Ekanite | Ca2ThSi8O20 | Tet. 4 2 2 : I4 2 2 |
| 9.EA.15 | Fluorapophyllite-(K) | KCa4(Si8O20)(F,OH) · 8H2O | Tet. 4/mmm (4/m 2/m 2/m) : P4/mnc |
| 9.EA.15 | Hydroxyapophyllite-(K) | KCa4(Si8O20)(OH,F) · 8H2O | Tet. |
| 9.EA.15 | Fluorapophyllite-(Na) | NaCa4(Si8O20)F · 8H2O | Orth. |
| 9.EA.20 | Magadiite | Na2Si14O29 · 11H2O | Mon. |
| 9.EA.25 | Dalyite | K2ZrSi6O15 | Tric. |
| 9.EA.25 | Davanite | K2TiSi6O15 | Tric. |
| 9.EA.30 | Sazhinite-(Ce) | Na2CeSi6O14•6H2O | |
| 9.EA.30 | Sazhinite-(La) | Na3La[Si6O15] · 2H2O | Orth. mm2 : Pmm2 |
| 9.EA.35 | Armstrongite | CaZr[Si6O15] · 3H2O | Mon. |
| 9.EA.40 | Okenite | Ca10Si18O46 · 18H2O | Tric. 1 : P1 |
| 9.EA.45 | Nekoite | Ca3Si6O15·7H2O | Tric. 1 : P1 |
| 9.EA.50 | Cavansite | Ca(VO)Si4O10 · 4H2O | Orth. mmm (2/m 2/m 2/m) |
| 9.EA.60 | Penkvilksite | Na4Ti2Si8O22 · 4H2O | Orth. mmm (2/m 2/m 2/m) : Pbcn |
| 9.EA.60 | Tumchaite | Na2Zr(Si4O11) · 2H2O | Mon. |
| 9.EA.65 | Nabesite | Na2BeSi4O10 · 4H2O | Orth. 2 2 2 : P21 21 21 |
| 9.EA.70 | Ajoite | (K,Na)Cu7AlSi9O24(OH)6 · 3H2O | Tric. |
| 9.EA.75 | Zeravshanite | Na2Cs4Zr3[Si18O45]*2H2O | Mon. 2/m : B2/b |
| 9.EA.80 | Bussyite-(Ce) | (Ce,REE)3(Na,H2O)6MnSi9Be5(O,OH)30F4 | Mon. 2/m : B2/b |
| 9.EA.85 | Plumbophyllite | Pb2Si4O10 · H2O | Orth. mmm (2/m 2/m 2/m) : Pbcn |
Related Minerals - Dana Grouping (8th Ed.)
| 74.3.7.1 | Cavansite | Ca(VO)Si4O10 · 4H2O | Orth. mmm (2/m 2/m 2/m) |
Related Minerals - Hey's Chemical Index of Minerals Grouping
| 14.14.1 | Cavansite | Ca(VO)Si4O10 · 4H2O | Orth. mmm (2/m 2/m 2/m) |
| 14.14.3 | Goldmanite | Ca3V3+2(SiO4)3 | Iso. |
| 14.14.4 | Haradaite | SrVSi2O7 | Orth. |
| 14.14.5 | Saneroite | NaMn2+5[Si5O14(OH)](VO3)(OH) | Tric. |
| 14.14.6 | Erlianite | (Fe,Mg)4(Fe,V)2Si6O15(OH,O)8 | Orth. |
| 14.14.7 | Eulytine | Bi4(SiO4)3 | Iso. 4 3m : I4 3d |
| 14.14.8 | Bismutoferrite | Fe3+2Bi(SiO4)2(OH) | Mon. m : Bm |
Other Information
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 Pentagonite
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 Pentagonite
mindat.org URL:
https://www.mindat.org/min-3152.html
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Specimens:
The following Pentagonite specimens are currently listed for sale on minfind.com.
Localities for Pentagonite
ⓘ - 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.
- 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).
All localities listed without proper references should be considered as questionable.
India | |
| Praszkier, T. & Siuda, R. (2007): The Lonavala Quarry, Pune District, Maharashtra, India. Mineralogical Record 38: 185-189 |
| 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) | |
| Amer.Min.(1973) 58, 405-411 and 412-424 |
Wagholi Quarries, Wagholi, Pune District, Maharashtra, India