Pentagonite (original) (raw)
A valid IMA mineral species
About PentagoniteHide
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Formula:
Ca(VO)Si4O10 · 4H2O
Specific Gravity:
2.33 (Calculated)
Crystal System:
Orthorhombic
Name:
For the pseudosymmetrical five-fold habit of the typical pentagonite twins.
Structurally related to plumbophyllite.
Ishida et al. (2009) suggest that cavansite is a low-temperature form and pentagonite a high-temperature form.
To distinguish Pentagonite and Cavansite one can compare the two under light with a strong blue component, like halogen or sunlight. The pentagonite is a very pure blue and the cavansite is green in comparison. The teal colour of Cavansite may not show up in photos but it is real. Please see: https://www.mindat.org/mesg-609416.html#609580
Unique IdentifiersHide
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Long-form identifier:
mindat:1:1:3152:9
a2613940-d664-4f08-99ec-dee3b0fd6629
IMA Classification of PentagoniteHide
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IMA Formula:
CaV4+OSi4O10 · 4H2O
Type description reference:
Classification of PentagoniteHide
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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
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.
| Symbol | Source | Reference |
|---|---|---|
| Ptg | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of PentagoniteHide
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Cleavage:
Distinct/Good
Good on {010}
Density:
2.33 g/cm3 (Calculated)
Optical Data of PentagoniteHide
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RI values:
_n_α = 1.533 _n_β = 1.544 _n_γ = 1.547
2V:
Measured: 50° , Calculated: 54°
δ = 0.014
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Dispersion:
r > v strong. Dispersion opposite to that of cavansite.
Optical Extinction:
X = b; Y = a; Z = c.
Comments:
X=Z= colourless
Y= blue
Chemistry of PentagoniteHide
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Mindat Formula:
Ca(VO)Si4O10 · 4H2O
Crystallography of PentagoniteHide
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Crystal System:
Orthorhombic
Class (H-M):
m _m_2 - 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)
Morphology:
Prismatic, bladed.
Twinning:
Cyclical by reflection across {110}, producing twinning at an angle near 72.7° ((110) ∧ (110)), and sometimes giving rise to fivelings.
Comment:
Space group Ccm21.
Crystal StructureHide
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| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0000317 | Pentagonite | Evans H T (1973) The crystal structures of cavansite and pentagonite American Mineralogist 58 412-424 |  |
1973 | 0 | 293 | |
| 0019265 | Pentagonite | Ishida N, Kimata M, Nishida N, Hatta T, Shimizu M, Akasaka T (2009) Polymorphic relation between cavanite and pentagonite: genetic implications of oxonium ion in cavansite Journal of Mineralogical and Petrological Sciences 104 241-252 | 2009 | Deccan basalts, Wagholi, India | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder DiffractionHide
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Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.071 Å | (100) |
| 3.920 Å | (100) |
| 3.755 Å | (100) |
| 8.298 Å | (70) |
| 3.500 Å | (36) |
| 2.569 Å | (36) |
| 4.446 Å | (25) |
Comments:
Owyhee Dam, Oregon, USA. Data from the type description.
Geological EnvironmentHide
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Geological Setting:
Fracture filling in tuffs and basalts.
Type Occurrence of PentagoniteHide
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General Appearance of Type Material:
Radiating greenish-blue prismatic crystals.
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 120584, 122769.
Geological Setting of Type Material:
Cavities and veinlets in basalt and vugs in tuff.
Associated Minerals at Type Locality:
Reference:
Staples, L.W., Evans, H.T., Jr., Lindsay, J.R. (1973): Cavansite and pentagonite, new dimorphous calcium vanadium silicate minerals from Oregon. American Mineralogist: 58: 405-411.
Synonyms of PentagoniteHide
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Other Language Names for PentagoniteHide
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Common AssociatesHide
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Associated Minerals Based on Photo Data:
Related Minerals - Strunz-mindat GroupingHide
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| 9.EA. | Bussyite-(Y) | (Y,REE,Ca)3(Na,Ca)6MnSi9Be5(O,OH,F)34 | Mon. 2 : _B_2 |
|---|---|---|---|
| 9.EA. | Fluorapophyllite-(NH₄) | NH4Ca4(Si8O20)F · 8H2O | Tet. 4/m m m _(_4/_m_2/_m_2/m ) : _P_4/m n c |
| 9.EA. | Hydroxymcglassonite-(K) | KSr4Si8O20(OH) · 8H2O | Tet. |
| 9.EA. | Miyawakiite-(Y) | ◻Y4Fe2(Si8O20)(CO3)4(H2O)3 | Tet. 4/m m m _(_4/_m_2/_m_2/m ) : _I_4/m c m |
| 9.EA.05 | Cuprorivaite | CaCuSi4O10 | Tet. 4/m m m _(_4/_m_2/_m_2/m ) : _P_4/n c c |
| 9.EA.05 | Gillespite | BaFe2+Si4O10 | Tet. 4/m m m _(_4/_m_2/_m_2/m ) : _P_4/n c c |
| 9.EA.05 | Effenbergerite | BaCuSi4O10 | Tet. 4/m m m _(_4/_m_2/_m_2/m ) : _P_4/n c c |
| 9.EA.05 | Wesselsite | SrCuSi4O10 | Tet. 4/m m m _(_4/_m_2/_m_2/m ) : _P_4/n c c |
| 9.EA.07 | Fluorapophyllite-(Cs) | CsCa4(Si8O20)F · 8H2O | Tet. |
| 9.EA.10 | Ekanite | Ca2ThSi8O20 | Tet. 422 : _I_422 |
| 9.EA.15 | Fluorapophyllite-(K) | KCa4(Si8O20)(F,OH) · 8H2O | Tet. 4/m m m _(_4/_m_2/_m_2/m ) : _P_4/m n c |
| 9.EA.15 | Hydroxyapophyllite-(K) | KCa4(Si8O20)(OH,F) · 8H2O | Tet. 4/m m m _(_4/_m_2/_m_2/m ) |
| 9.EA.15 | Fluorapophyllite-(Na) | NaCa4(Si8O20)F · 8H2O | Orth. |
| 9.EA.20 | Magadiite | Na2Si14O29 · 11H2O | Orth. m _m_2 : F d _d_2 |
| 9.EA.25 | Dalyite | K2ZrSi6O15 | Tric. 1 : _P_1 |
| 9.EA.25 | Davanite | K2TiSi6O15 | Tric. |
| 9.EA.30 | Sazhinite-(Ce) | Na3CeSi6O15 · 2H2O | Orth. m _m_2 : P m _m_2 |
| 9.EA.30 | Sazhinite-(La) | Na3La[Si6O15] · 2H2O | Orth. m _m_2 : P m _m_2 |
| 9.EA.35 | Armstrongite | CaZr[Si6O15] · 3H2O | Mon. 2/m : _B_2/m |
| 9.EA.40 | Okenite | Ca10Si18O46 · 18H2O | Tric. 1 : _P_1 |
| 9.EA.45 | Nekoite | Ca3Si6O15 · 7H2O | Tric. 1 : _P_1 |
| 9.EA.45 | Perettiite-(Y) | Y2Mn4FeSi2B8O24 | Orth. m m m _(_2/_m_2/_m_2/m ) : P m n a |
| 9.EA.45 | Badakhshanite-(Y) | Y2Mn4Al(Si2B7BeO24) | Orth. m m m _(_2/_m_2/_m_2/m ) : P n m a |
| 9.EA.47 | Shlykovite | KCa[Si4O9(OH)] · 3H2O | Mon. 2/m : _P_21/b |
| 9.EA.50 | Cavansite | Ca(VO)Si4O10 · 4H2O | Orth. m m m _(_2/_m_2/_m_2/m ) |
| 9.EA.50 | Diegogattaite | Na2CaCu2Si8O20 · H2O | Mon. 2/m : _B_2/m |
| 9.EA.52 | Yangite | PbMnSi3O8 · H2O | Tric. 1 : _P_1 |
| 9.EA.60 | Penkvilksite | Na4Ti2Si8O22 · 4H2O | Orth. m m m _(_2/_m_2/_m_2/m ) : P b c n |
| 9.EA.60 | Tumchaite | Na2Zr(Si4O11) · 2H2O | Mon. 2/m : _P_21/b |
| 9.EA.65 | Nabesite | Na2BeSi4O10 · 4H2O | Orth. 222 : _P_212121 |
| 9.EA.70 | Ajoite | (K,Na)Cu7AlSi9O24(OH)6 · 3H2O | Tric. |
| 9.EA.75 | Zeravshanite | Na2Cs4Zr3[Si18O45]*2H2O | Mon. 2/m : _B_2/b |
| 9.EA.80 | Bussyite-(Ce) | (Ce,REE)3(Na,H2O)6MnSi9Be5(O,OH)30F4 | Mon. 2/m : _B_2/b |
| 9.EA.85 | Plumbophyllite | Pb2Si4O10 · H2O | Orth. m m m _(_2/_m_2/_m_2/m ) : P b c n |
Other InformationHide
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Notes:
Soluble in acids with difficulty. In HNO3, the blue color bleaches out and turns olive brown. A fine white crystalline precipitate is slowly formed on a microscope slide when the minerals are heated in dilute H2SO4.
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 PentagoniteHide
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References for PentagoniteHide
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Reference List:
Ishida, Naoya, Kimata, Mitsuyoshi, Nishida, Norimasa, Hatta, Tamao, Shimizu, Masahiro, Akasaka, Takeshi (2009) Polymorphic relation between cavansite and pentagonite: Genetic implications of oxonium ion in cavansite. Journal of Mineralogical and Petrological Sciences, 104 (4) 241-252 doi:10.2465/jmps.070724b
Localities for PentagoniteHide
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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
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