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Tokkoite

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Formula:
K2Ca4[Si7O18(OH)](OH,F)
Previous formula: K2Ca4Si7O17(O,OH,F)4
System:
Triclinic
Colour:
Light yellow
Lustre:
Vitreous
Hardness:
4 - 5
Name:
Named after its discovery locality, Davan stream near Vislopolovka village, between the Chara and Tokko Rivers, Saha Republic, Russia.
Isostructural with:
Chemically similar to mountainite, hydroxyapophyllite-(K), shlykovite, rhodesite, and cryptophyllite.

The difference from tinaksite is in (1) greater lattice constants (mainly the parameter b), (2) longer distances, (3) longer M1-M3 and O20-O2 bonds, and (4) more distorted M1 polyhedron. Contains significant admixture of Fe3+.


Classification of Tokkoite

Approved
Approval Year:
1985
9.DG.75

9 : SILICATES (Germanates)
D : Inosilicates
G : Inosilicates with 3-periodic single and multiple chains
67.2.1.2

67 : INOSILICATES Unbranched Chains with W > 2
2 : Unbranched Chains with W>2 with W=5
14.6.5

14 : Silicates not Containing Aluminum
6 : Silicates of Ca with alkali or Mg or both

Physical Properties of Tokkoite

Vitreous
Diaphaneity (Transparency):
Transparent
Colour:
Light yellow
Hardness (Mohs):
4 - 5

Optical Data of Tokkoite

Type:
Biaxial (+)
RI values:
nα = 1.570 nγ = 1.577
2V:
Measured: 38°
Max Birefringence:
δ = 0.007
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r > v

Chemical Properties of Tokkoite

Formula:
K2Ca4[Si7O18(OH)](OH,F)

Previous formula: K2Ca4Si7O17(O,OH,F)4
IMA Formula:
K2Ca4Si7O18(OH)F
Elements listed in formula:
Common Impurities:
Ti,Fe,Mn,Mg,Na,H2O

Crystallography of Tokkoite

Crystal System:
Triclinic
Cell Parameters:
a = 10.43 Å, b = 12.51 Å, c = 7.11 Å
α = 89.92°, β = 99.75°, γ = 92.89°
Ratio:
a:b:c = 0.834 : 1 : 0.568
Unit Cell Volume:
V 913.12 ų (Calculated from Unit Cell)
Comment:
mean parameters concerning the structure refinement (Lacalamita et al., 2016): a~10.423, b~12.477, c~7.112, α~89.92, β~99.68, γ~92.97, V~910.5

Type Occurrence of Tokkoite

Relationship of Tokkoite to other Species

9.DG.05BustamiteCaMn2+(Si2O6)
9.DG.05FerrobustamiteCaFe2+(Si2O6)
9.DG.05PectoliteNaCa2Si3O8(OH)
9.DG.05SeranditeNaMn22+Si3O8(OH)
9.DG.05WollastoniteCaSiO3
9.DG.05Wollastonite-1ACaSiO3
9.DG.07CascanditeCa(Sc,Fe3+)(HSi3O9)
9.DG.08Plombièrite[Ca4Si6O16(OH)2 · 2H2O]·(Ca·5H2O)
9.DG.10Clinotobermorite[Ca4Si6O17 · 2H2O]·(Ca·3H2O)
9.DG.10RiversideiteCa5(HSi3O9)2 · 2H2O
9.DG.10Tobermorite[Ca4Si6O17 · 2H2O]·(Ca·3H2O)
9.DG.15FoshagiteCa4(Si3O9)(OH)2
9.DG.20JenniteCa9(Si3O9)2(OH)8 · 8H2O
9.DG.25ParaumbiteK3Zr2H(Si3O9)2 · nH2O
9.DG.25UmbiteK2(Zr,Ti)Si3O9 · H2O
9.DG.30SørenseniteNa4SnBe2Si6O16(OH)4
9.DG.35XonotliteCa6(Si6O17)(OH)2
9.DG.40HillebranditeCa2(SiO3)(OH)2
9.DG.45ZoriteNa8(Ti,Nb)5(Si6O17)2(OH,O)5 · 14H2O
9.DG.45ChivruaiiteCa4(Ti,Nb)5(Si6O17)2(OH,O)5 · 13-14H2O
9.DG.50Haineaultite(Na,Ca)5Ca(Ti,Nb)5(Si6O17)2(OH,F)8 · 5H2O
9.DG.55EpididymiteNa2Be2Si6O15 · H2O
9.DG.60EudidymiteNa2Be2Si6O15 · H2O
9.DG.65ElpiditeNa2ZrSi6O15 · 3H2O
9.DG.70Fenaksite(K,Na)4(Fe,Mn)2(Si4O10)2(OH,F)
9.DG.70LitidioniteCuNaKSi4O10
9.DG.70ManaksiteKNaMnSi4O10
9.DG.75TinaksiteK2Na(Ca,Mn2+)2Ti[O|Si7O18(OH)]
9.DG.75SenkevichiteCsKNaCa2Ti[O|Si7O18(OH)]
9.DG.80CanasiteK3Na3Ca5Si12O30(OH)4
9.DG.80FluorcanasiteK3Na3Ca5Si12O30F4 · H2O
9.DG.85MiseriteK1.5-x(Ca,Y,REE)5(Si6O15)(Si2O7)(OH,F)2 · yH2O
9.DG.90FrankameniteK3Na3Ca5(Si12O30)(F,OH)4 · H2O
9.DG.92Charoite(K,Sr)15-16(Ca,Na)32[Si6O11(O,OH)6]2[Si12O18(O,OH)12]2[Si17O25(O,OH)18]2(OH,F)4 · ~3H2O
9.DG.95YuksporiteK4(Ca,Na)14(Sr,Ba)2(◻,Mn,Fe)(Ti,Nb)4(O,OH)4(Si6O17)2(Si2O7)3(H2O,OH)3
9.DG.97Eveslogite(Na,K,Ca,Sr,Ba)48 [(Ti,Nb,Mn,Fe2+)12Si48O144(OH)12](F,OH,Cl)14
14.6.1CombeiteNa2Ca2(Si6O18)0.5
14.6.2PectoliteNaCa2Si3O8(OH)
14.6.3Pectolite-M2abcNaCa2[HSi3O9]
14.6.4DenisoviteCa2(K,Na)Si3O8(F,OH)2
14.6.6MountainiteKNa2Ca2[Si8O19(OH)] · 6H2O
14.6.7RhodesiteKHCa2Si8O19 · 5H2O
14.6.8MiseriteK1.5-x(Ca,Y,REE)5(Si6O15)(Si2O7)(OH,F)2 · yH2O
14.6.9ÅkermaniteCa2Mg(Si2O7)
14.6.10MonticelliteCaMgSiO4
14.6.11MerwiniteCa3Mg(SiO4)2
14.6.12DiopsideCaMgSi2O6
14.6.13Tremolite☐{Ca2}{Mg5}(Si8O22)(OH)2

Other Names for Tokkoite

Name in Other Languages:
German:Tokkoit
Spanish:Tokkoita

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 Tokkoite

Reference List:
Mineralogicheskii Zhurnal, Kiev (1986): 8(3): 85-89.

American Mineralogist (1988): 73: 196.

Zeitschrift für Kristallographie: 189: 195-204.

Lacalamita, M., Mesto, E., Kaneva, E., Scordari, F., Pedrazzi, G., Vladkyn, N., Schingaro, E. (2016): Structure refinement and crystal chemistry of tokkoite and tinaksite from Murun massif (Russia). Mineralogical Magazine: 80 (in press); http://forum.amiminerals.it/viewtopic.php?f=5&t=12645 (2016)

Internet Links for Tokkoite

mindat.org URL:
https://www.mindat.org/min-3989.html
Please feel free to link to this page.

Localities for Tokkoite

(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? 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.
Russia (TL)
 
  • Eastern-Siberian Region
    • Sakha Republic (Saha Republic; Yakutia)
      • Aldan Shield
        • Chara and Tokko Rivers Confluence
          • Murunskii Massif
            • Sirenevyi Kamen' Deposit
Pekov, I. (1998) Minerals First discovered on the territory of the former Soviet Union 369p. Ocean Pictures, Moscow
Mineral and/or Locality  
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