Mountainite
A valid IMA mineral species - grandfathered
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About Mountainite
Edgar Donald Mountain
Formula:
KNa2Ca2[Si8O19(OH)] · 6H2O
Colour:
white
Hardness:
3
Specific Gravity:
2.36
Crystal System:
Monoclinic
Member of:
Name:
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.
Unique Identifiers
Mindat ID:
2795
Long-form identifier:
mindat:1:1:2795:9
Similar Names
IMA Classification of Mountainite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
KNa2Ca2[Si8O19(OH)]·6H2O
First published:
1957
Classification of Mountainite
9.GG.10
9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H2O; zeolite family
G : Unclassified zeolites
9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H2O; zeolite family
G : Unclassified zeolites
77.2.3.1
77 : TECTOSILICATES Zeolites
2 : Zeolite group - related species
77 : TECTOSILICATES Zeolites
2 : Zeolite group - related species
14.6.6
14 : Silicates not Containing Aluminum
6 : Silicates of Ca with alkali or Mg or both
14 : Silicates not Containing Aluminum
6 : Silicates of Ca with alkali or Mg or both
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Mtn | 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 Mountainite
Transparency:
Transparent, Translucent
Colour:
White
Streak:
White
Hardness:
3 on Mohs scale
Cleavage:
Poor/Indistinct
one doubtful in prism zone.
one doubtful in prism zone.
Density:
2.36 g/cm3 (Measured) 2.47 g/cm3 (Calculated)
Optical Data of Mountainite
Type:
Biaxial (+)
RI values:
nα = 1.500 - 1.504 nβ = 1.505 - 1.510 nγ = 1.513 - 1.519
2V:
Calculated: 78° to 80°
Max. Birefringence:
δ = 0.013 - 0.015
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Low (negative)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
relatively strong
Chemistry of Mountainite
Mindat Formula:
KNa2Ca2[Si8O19(OH)] · 6H2O
Element Weights:
Common Impurities:
Al,Mg,C
Crystallography of Mountainite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P2/b
Cell Parameters:
a = 13.704(2) Å, b = 6.5760(10) Å, c = 13.751(2) Å
β = 105.752(10)°
β = 105.752(10)°
Ratio:
a:b:c = 2.084 : 1 : 2.091
Unit Cell V:
1192.7 ų
Z:
2
Morphology:
As matted laths and fibers, elongated along [010], forming small rosettes, to 2 mm.
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0011131 | Mountainite | Zubkova N V, Pekov I V, Pushcharovsky D Y, Chukanov N V (2009) The crystal structure and refined formula of mountainite, KNa2Ca2[Si8O19(OH)]*6H2O Zeitschrift fur Kristallographie 224 389-396 | 2009 | Yubileinaya pegmatite, Lovozero alkaline complex, Kola Peninsula, Russia | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.94 Å | (vvs) |
| 6.6 Å | (vs) |
| 13.1 Å | (s) |
| 4.67 Å | (s) |
| 2.80 Å | (ms) |
| 1.967 Å | (ms) |
| 4.18 Å | (m) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 3a: Earth’s earliest Hadean crust | >4.50 |
| 7 : Ultramafic igneous rocks | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Type Occurrence of Mountainite
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 Mountainite
Relationship of Mountainite to other Species
Member of:
Other Members of Zeolite Group:
| Alflarsenite | NaCa2Be3Si4O13(OH) · 2H2O | Mon. 2 : P21 |
| Amicite | K2Na2Al4Si4O16 · 5H2O | Mon. 2 |
| Ammonioleucite | (NH4)(AlSi2O6) | Tet. 4/m : I41/a |
| Analcime | Na(AlSi2O6) · H2O | Tric. 1 : P1 |
| Arzamastsevite | K6Al5Si6O20(OH)4Cl | Tet. 42m : I42m |
| Bellbergite | (K,Ba,Sr)2Sr2Ca2(Ca,Na)4[Al3Si3O12]6 · 30H2O | Hex. |
| Bikitaite | LiAlSi2O6 · H2O | Tric. 1 : P1 |
| Boggsite | Ca8Na3(Si,Al)96O192 · 70H2O | Orth. mmm(2/m2/m2/m) : Imma |
| Brewsterite Subgroup | Zeolite Group. | |
| Chabazite-Levyne Subgroup | M[Al2Si4O12] · 6H2O | |
| Chiavennite | CaMnBe2Si5O13(OH)2 · 2H2O | Mon. 2/m : P21/b |
| Clinoptilolite Subgroup | (Na/Ca/K)3-6[Al6-7Si29-30O72] · 20H2O | |
| Cowlesite | CaAl2Si3O10 · 6H2O | Orth. mmm(2/m2/m2/m) |
| Dachiardite Subgroup | Zeolite Group. | |
| Direnzoite | NaK6MgCa2(Al13Si47O120) · 36H2O | Orth. mmm(2/m2/m2/m) : Pmmn |
| Edingtonite | Ba[Al2Si3O10] · 4H2O | Orth. 222 : P212121 |
| Epistilbite | CaAl2Si6O16 · 5H2O | Mon. |
| Erionite Subgroup | M2[Al4Si14O36] · 15H2O | |
| Fabrièsite | Na3Al3Si3O12 · 2H2O | Orth. mm2 : Pmm2 |
| Faujasite Subgroup | M3.5[Al7Si17O48] · 32H2O | |
| Ferrierite Subgroup | Name used for unanalysed specimens that could be either ferrierite-K, ferrierite-Mg, ... | |
| Ferrochiavennite | Ca1-2Fe[(Si,Al,Be)5Be2O13(OH)2] · 2H2O | Mon. 2/m : P21/b |
| Flörkeite | (K3Ca2Na)[Al8Si8O32] · 12H2O | Tric. 1 : P1 |
| Garronite Subgroup | ||
| Gaultite | Na4Zn2Si7O18 · 5H2O | Orth. mm2 : Fdd2 |
| Gismondine Subgroup | Zeolite Group. | |
| Gmelinite Subgroup | In 1997, gmelinite was split into Gmelinite-Ca, Gmelinite-Na and Gmelinite-K. | |
| Gobbinsite | Na5(Si11Al5)O32 · 11H2O | Orth. mmm(2/m2/m2/m) : Pnma |
| Goosecreekite | Ca[Al2Si6O16] · 5H2O | Mon. 2 : P21 |
| Gottardiite | Na3Mg3Ca5Al19Si117O272 · 93H2O | Orth. mmm(2/m2/m2/m) : Cmca |
| Heulandite Subgroup | (Na/Ca/K)5-6[Al8-9 Si27-28 O72] · nH2O | |
| Hsianghualite | Ca3Li2(Be3Si3O12)F2 | Iso. 23 : I213 |
| Kalborsite | K6Al4BSi6O20(OH)4Cl | Tet. 42m : P421c |
| Kirchhoffite | Cs(BSi2O6) | Tet. 4/mmm(4/m2/m2/m) : I41/acd |
| Laumontite | CaAl2Si4O12 · 4H2O | Mon. 2/m : B2/m |
| Leucite | K(AlSi2O6) | Tet. 4/m : I41/a |
| Limousinite | BaCa[Be4P4O16] · 6H2O | Mon. 2/m : P21/b |
| Lithosite | K6Al4Si8O25 · 2H2O | Mon. |
| Loomisite | Ba[Be2P2O8] · H2O | Mon. m |
| Lovdarite | K2Na6Be4Si14O36 · 9H2O | Orth. mm2 |
| Maricopaite | Pb7Ca2(Si,Al)48O100 · 32H2O | Orth. |
| Martinandresite | Ba2(Al4Si12O32) · 10H2O | Orth. mmm(2/m2/m2/m) : Pmmn |
| Mazzite Subgroup | Zeolite Group. | |
| Meierite | Ba44Si66Al30O192Cl25(OH)33 | Iso. m3m(4/m32/m) : Im3m |
| Merlinoite | K5Ca2(Si23Al9)O64 · 24H2O | Orth. mmm(2/m2/m2/m) : Immm |
| Montesommaite | (K,Na)9Al9Si23O64 · 10H2O | Orth. mm2 : Fdd2 |
| Mordenite | (Na2,Ca,K2)4(Al8Si40)O96 · 28H2O | Orth. |
| Mutinaite | Na3Ca4Si85Al11O192 · 60H2O | Orth. mmm(2/m2/m2/m) : Pnma |
| Nabesite | Na2BeSi4O10 · 4H2O | Orth. 222 : P212121 |
| Natrolite Subgroup | A subgroup of the Zeolite Group. | |
| Offretite | KCaMg(Si13Al5)O36 · 15H2O | Hex. 6m2 : P6m2 |
| Pahasapaite | Li8(Ca,Li,K)10.5Be24(PO4)24 · 38H2O | Iso. 23 : I23 |
| Parthéite | Ca2(Si4Al4) O15 (OH)2 · 4H2O | Mon. 2/m : B2/b |
| Paulingite Subgroup | Paulingite was originally described in 1960. | |
| Perlialite | K9Na(Ca,Sr)[Al2Si4O12]6 · 15H2O | Hex. 6/mmm(6/m2/m2/m) : P6/mmm |
| Phillipsite Subgroup | (Ca0.5,K,Na,Ba0.5)4-7[Al4-7Si12-9O32] . 12H2O | |
| Pollucite | (Cs,Na)2(Al2Si4O12) · 2H2O | Iso. m3m(4/m32/m) : Ia3d |
| Roggianite | Ca2Be(OH)2Al2Si4O13 · 2.5H2O | Tet. 4/mmm(4/m2/m2/m) : I4/mcm |
| Rongibbsite | Pb2(Si4Al)O11(OH) | Mon. 2/m : B2/m |
| Stilbite Subgroup | M6-7[Al8-9Si27-28O72] · nH2O | |
| Terranovaite | (Na,Ca)8(Si68Al12)O160 · 29H2O | Orth. |
| Thomsonite Subgroup | The large majority of "thomsonite" is thomsonite-Ca. | |
| Thornasite | Na12Th4+3(Si8O19)4 · 18H2O | Trig. 3m : R3m |
| Tschernichite | (Ca,Na2)[Al2Si4O12] · 4-8H2O | Tet. 4/mmm(4/m2/m2/m) : P4/mmm |
| Tschörtnerite | Ca4(Ca,Sr,K,Ba)3Cu3[Al3Si3O12]4(OH)8 · nH2O | Iso. m3m(4/m32/m) : Fm3m |
| 'UM1996-38-SiO:AlCaHNa' | Na-Ca-Al-Si-O-H | |
| 'UM1999-33-SiO:AlHKNa' | K7Na5Al12Si20O64 · 24H2O | |
| 'UM2002-40-SiO:AlCaHKMgNa' | (Mg,Ca,Na,K)7.5(Al12.8Si51.2)O128 · 65H2O | Tet. 422 : P4122 |
| 'Unnamed (Ca analogue of Merlinoite)' | (Ca,K,Na)5(Ca,Ba)2Al9Si23O64 · 23H2O ? | |
| Wairakite | Ca(Al2Si4O12) · 2H2O | Mon. 2/m : B2/m |
| Weinebeneite | CaBe3(PO4)2(OH)2 · 4H2O | Mon. m : Bb |
| Wenkite | (Ba,K)4(Ca,Na)6[(Si,Al)20O39(OH)2](SO4)3 · 0.5H2O | Hex. 6m2 : P62m |
| Wilancookite | (Ba5Li2◻)Ba6Be24P24O96 · 26H2O | Iso. 23 : I23 |
| Willhendersonite | KCa[Al3Si3O12] · 5H2O | Tric. 1 : P1 |
| Yugawaralite | CaAl2Si6O16 · 4H2O | Mon. m : Pb |
Common Associates
Associations Based on Photo Data:
| 8 photos of Mountainite associated with Raite | Mn2+Mn2+2Na2(◻1.75Ti0.25)Si8O20(OH)2(H2O)4 · Na(H2O)6 |
| 5 photos of Mountainite associated with Vitusite-(Ce) | Na3(Ce,La,Nd)(PO4)2 |
| 4 photos of Mountainite associated with Steenstrupine-(Ce) | Na14Mn2+2Fe3+2Ce6Zr(Si6O18)2(PO4)6(PO3OH)(OH)2 · 2H2O |
| 4 photos of Mountainite associated with Natrolite | Na2Al2Si3O10 · 2H2O |
| 3 photos of Mountainite associated with Magnesio-arfvedsonite | NaNa2(Mg4Fe3+)(Si8O22)(OH)2 |
| 2 photos of Mountainite associated with Sazhinite-(Ce) | Na3CeSi6O15 · 2H2O |
| 1 photo of Mountainite associated with Leucosphenite | BaNa4Ti2B2Si10O30 |
| 1 photo of Mountainite associated with Zorite | Na8(Ti,Nb)5(Si6O17)2(OH,O)5 · 14H2O |
| 1 photo of Mountainite associated with Aegirine | NaFe3+Si2O6 |
Related Minerals - Strunz-mindat Grouping
| 9.GG.05 | Cowlesite | CaAl2Si3O10 · 6H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 4.7739% | 1,480 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
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.
Internet Links for Mountainite
mindat.org URL:
https://www.mindat.org/min-2795.html
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References for Mountainite
Reference List:
Gard, J. A., Taylor, H. F. W., Chalmers, R. A. (1957) An investigation of two new minerals: rhodesite and mountainite. Mineralogical Magazine and Journal of the Mineralogical Society, 31 (239). 611-623 doi:10.1180/minmag.1957.31.239.02
Localities for Mountainite
Showing 5 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and 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).
All localities listed without proper references should be considered as questionable.
Germany | |
| Tschernich (1992) |
Romania | |
| Pascal et al. (2001) |
Russia | |
| Pluth et al. (1997) +2 other references |
South Africa (TL) | |
| Gard et al. (1957) |
USA | |
| Barnes et al. (1972) +3 other references |
Quick NavTopAbout MountainiteUnique IdentifiersSimilar NamesIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesRelationshipsCommon AssociatesStrunz-MindatRadioactivityOther InformationInternet Links References Localities Locality List
Bultfontein Mine, KEM JV Mine, Kimberley, Sol Plaatje Local Municipality, Frances Baard District Municipality, Northern Cape, South Africa