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About MountainiteHide

Edgar Donald Mountain
KNa2Ca2[Si8O19(OH)] · 6H2O
Specific Gravity:
Crystal System:
Named by J.A. Gard, H.F.W. Taylor, and R.A. Chalmers in 1957 for Edgar Donald Mountain (2 April 1901 – 30 April 1985), Professor of Geology, Rhodes University, Grahamstown, South Africa, who provided the first specimens for investigation.
Closely related to cryptophyllite and shlykovite.

Classification of MountainiteHide

Approved, 'Grandfathered' (first described prior to 1959)
First Published:

9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H2O; zeolite family
G : Unclassified zeolites

2 : Zeolite group - related species

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

Physical Properties of MountainiteHide

Transparent, Translucent
one doubtful in prism zone.
2.36 g/cm3 (Measured)    2.47 g/cm3 (Calculated)

Optical Data of MountainiteHide

Biaxial (+)
RI values:
nα = 1.500 - 1.504 nβ = 1.505 - 1.510 nγ = 1.513 - 1.519
Calculated: 78° to 80°
Max Birefringence:
δ = 0.013 - 0.015
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
relatively strong

Chemical Properties of MountainiteHide

KNa2Ca2[Si8O19(OH)] · 6H2O
Common Impurities:

Crystallography of MountainiteHide

Crystal System:
Class (H-M):
2/m - Prismatic
Space Group:
Cell Parameters:
a = 13.704(2) Å, b = 6.5760(10) Å, c = 13.751(2) Å
β = 105.752(10)°
a:b:c = 2.084 : 1 : 2.091
Unit Cell V:
1192.7 ų
As matted laths and fibers, elongated along [010], forming small rosettes, to 2 mm.

Type Occurrence of MountainiteHide

General Appearance of Type Material:
silky white fibers
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1957,369; National Museum of Natural History, Washington, D.C., USA, 114792.
Geological Setting of Type Material:
Kimberlite pipe
Associated Minerals at Type Locality:

Other Language Names for MountainiteHide


Common AssociatesHide

Associated Minerals Based on Photo Data:
Vitusite-(Ce)4 photos of Mountainite associated with Vitusite-(Ce) on
Steenstrupine-(Ce)4 photos of Mountainite associated with Steenstrupine-(Ce) on
Natrolite4 photos of Mountainite associated with Natrolite on
Sazhinite-(Ce)2 photos of Mountainite associated with Sazhinite-(Ce) on
Magnesio-arfvedsonite2 photos of Mountainite associated with Magnesio-arfvedsonite on
Raite2 photos of Mountainite associated with Raite on

Related Minerals - Nickel-Strunz GroupingHide

9.GG.05CowlesiteCaAl2Si3O10 · 6H2OOrth.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

14.6.1CombeiteNa4.5Ca3.5Si6O17.5(OH)0.5Trig. 3m (3 2/m) : R3m
14.6.2PectoliteNaCa2Si3O8(OH)Tric. 1 : P1
14.6.7RhodesiteKHCa2Si8O19 · 5H2OOrth. mmm (2/m 2/m 2/m)
14.6.8MiseriteK1.5-x(Ca,Y,REE)5(Si6O15)(Si2O7)(OH,F)2 · yH2OTric.
14.6.9ÅkermaniteCa2Mg(Si2O7)Tet. 4 2m : P4 21m
14.6.11MerwiniteCa3Mg(SiO4)2Mon. 2/m : P21/b
14.6.12DiopsideCaMgSi2O6Mon. 2/m : B2/b
14.6.13Tremolite☐{Ca2}{Mg5}(Si8O22)(OH)2Mon. 2/m : B2/m

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 MountainiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Gard, J.A., Taylor, H.F.W., Chalmers, R.A. (1957) An investigation of two new minerals: rhodesite and mountainite. Mineralogical Magazine: 31: 611-623.
Fleischer, M. (1958) New mineral names. American Mineralogist: 43: 623-626.
Bussen, I.V., Latysheva, L.G., Men'shikov, Y.P., Mer'kov, A.N., Romanova, T.S., Sakharov, A.S. (1973) First find of mountainite in the Soviet Union. Doklady Akademii Nauk SSSR: 210: 674-677. (in Russian)
Zubkova, N.V., Pekov, I.V., Pushcharovsky, D.Yu., Chukanov N.V. (2009) The crystal structure and refined formula of mountainite. Zeitschrift für Kristallographie: 224: 389-396.

Internet Links for MountainiteHide

Localities for MountainiteHide

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.
  • Baden-Württemberg
    • Hegau
      • Immendingen
Tschernich, R. (1992), Zeolites of the World, p.42
  • Hunedoara
    • Hunedoara
The Canadian Mineralogist Vol. 39, pp. 1405-1434 (2001)
  • Murmansk Oblast
    • Lovozero Massif
      • Karnasurt Mt
Pekov, I. (1998) Minerals First discovered on the territory of the former Soviet Union 369p. Ocean Pictures, Moscow; Zubkova, N. V., Pekov, I. V., Pushcharovsky, D. Y., & Chukanov, N. V. (2009). The crystal structure and refined formula of mountainite, KNa2Ca2 [Si8O19 (OH)]⊙ 6 H2O. Zeitschrift für Kristallographie, 224(8), 389-396.; Pluth, J. J., Smith, J. V., Pushcharovsky, D. Y., Semenov, E. I., Bram, A., Riekel, C., ... & Broach, R. W. (1997). Third-generation synchrotron x-ray diffraction of 6-μm crystal of raite,≈ Na3Mn3Ti0. 25Si8O20 (OH) 2⋅ 10H2O, opens up new chemistry and physics of low-temperature minerals. Proceedings of the National Academy of Sciences, 94(23), 12263-12267.
South Africa (TL)
  • Northern Cape
    • Francis Baard District
      • Kimberley
        • KEM JV Mine (Kimberley Ekapa Mining Joint Venture mine; Kimberley Underground mine)
Gard J A, Taylor H F W, Chalmers R A (1957) An investigation of two new minerals: rhodesite and mountainite. Mineralogical Magazine 31, 611-623
  • California
    • Trinity Co.
      • Klamath Mts
        • Trinity Mts
          • Halls Gulch Mining District
            • Wildcat Peak
Barnes, I., J.B. Rapp & J.R. O’Neil (1972), Metamorphic assemblages and the direction of flow of metamorphic fluids in four instances of serpentinization: Contributions to Mineralogy and Petrology: 35: 264; Pemberton, H. Earl (1983), Minerals of California; Van Nostrand Reinholt Press: 442;
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