Armstrongite
A valid IMA mineral species
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About Armstrongite
Neil Armstrong
Formula:
CaZr[Si6O15] · 3H2O
Colour:
Dark to light brown
Lustre:
Vitreous
Hardness:
4½
Specific Gravity:
2.562 - 2.593
Crystal System:
Monoclinic
Name:
Named after Neil Alden Armstrong (5 August 1930, Wapakoneta, Ohio, USA - 25 August 2012, Cincinnati, Ohio, USA), American astronaut and aeronautical engineer. He was the first person to walk on the Moon.
This page provides mineralogical data about Armstrongite.
Unique Identifiers
Mindat ID:
344
Long-form identifier:
mindat:1:1:344:7
IMA Classification of Armstrongite
Approved
IMA Formula:
CaZr4+Si6O15·2H2O
Approval year:
1972
First published:
1973
Classification of Armstrongite
9.EA.35
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
72.5.4.1
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
5 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with corrugated and complex layers
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
5 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with corrugated and complex layers
14.10.22
14 : Silicates not Containing Aluminum
10 : Silicates of Zr or Hf
14 : Silicates not Containing Aluminum
10 : Silicates of Zr or Hf
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 |
|---|---|---|
| Asg | 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 Armstrongite
Vitreous
Transparency:
Translucent
Colour:
Dark to light brown
Streak:
Brownish white
Hardness:
4½ on Mohs scale
Hardness:
VHN100=310 - 330 - Vickers
Tenacity:
Very brittle
Cleavage:
Very Good
Perfect on {001}
Good on {100}
Perfect on {001}
Good on {100}
Density:
2.562 - 2.593 g/cm3 (Measured) 2.71 g/cm3 (Calculated)
Optical Data of Armstrongite
Type:
Biaxial (-)
RI values:
nα = 1.563 nβ = 1.569 nγ = 1.573
Max. Birefringence:
δ = 0.010
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:
Moderate (positive)
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.
No measured or calculated 2V is on file for this mineral, so the value used here (78°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
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.
No measured or calculated 2V is on file for this mineral, so the value used here (78°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
strong r < v
Chemistry of Armstrongite
Mindat Formula:
CaZr[Si6O15] · 3H2O
Element Weights:
Common Impurities:
Ti,Al,Y,TR,Fe,Mg,Na,K
Crystallography of Armstrongite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C2/m
Cell Parameters:
a = 14.04 Å, b = 14.16 Å, c = 7.81 Å
β = 109.55°
β = 109.55°
Ratio:
a:b:c = 0.992 : 1 : 0.552
Unit Cell V:
1,463.17 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Crystals to 2cm, aggregates
Twinning:
Polysynthetic, by rotation on [100]
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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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) |
|---|---|---|---|---|---|---|---|
| 0020417 | Armstrongite | Mesto E, Kaneva E, Schingaro E, Vladykin N, Lacalamita M, Scordari F (2014) Armstrongite from Khan Bogdo (Mongolia): Crystal structure determination and implications for zeolite-like cation exchange properties American Mineralogist 99 2424-2432 | 2014 | Khan Bogdo deposit, southern Gobi Desert, Gobi, Mongolia | 0 | 293 | |
| 0019061 | Armstrongite | Kabalov Y K, Zubkova N V, Pushcharovsky D Y, Schneider J, Sapozhnikov A N (2000) Powder Rietveld refinement of armstrongite, CaZr[Si6O15]*3H2O Zeitschrift fur Kristallographie 215 757-761 | 2000 | granite pegmatites and alkaline granites in Mongolia | 0 | 293 | |
| 0014184 | Armstrongite | Kashaev A A, Sapozhnikov A N (1978) Crystal structure of armstrongite Kristallografiya 23 956-961 | 1978 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.26 Å | (100) |
| 3.05 Å | (100) |
| 6.60 Å | (90) |
| 3.80 Å | (90) |
| 7.05 Å | (50) |
| 2.995 Å | (50) |
| 1.947 Å | (50) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Geological Setting:
Alkalic granites
Type Occurrence of Armstrongite
General Appearance of Type Material:
As columnar crystals elongated along [010], to 2 cm, and as tangled-fibrous aggregates
Place of Conservation of Type Material:
A.E. Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia.
Geological Setting of Type Material:
In schlieren of alkalic granite pegmatite, at the contact of arfvedsonite-bearing granite with xenoliths of felsic volcanic rock.
Associated Minerals at Type Locality:
Synonyms of Armstrongite
Other Language Names for Armstrongite
Dutch:Armstrongiet
French:Armstrongite
German:Armstrongit
Norwegian:Armstrongitt
Russian:Армстронгит
Spanish:Armstrongita
Common Associates
Associations Based on Photo Data:
| 14 photos of Armstrongite associated with Aegirine | NaFe3+Si2O6 |
| 4 photos of Armstrongite associated with Quartz | SiO2 |
| 3 photos of Armstrongite associated with Orthoclase | K(AlSi3O8) |
| 2 photos of Armstrongite associated with Gittinsite | CaZrSi2O7 |
| 1 photo of Armstrongite associated with 'Calcium-bearing Elpidite' | (Na,Ca)2ZrSi6O15 · 3H2O |
| 1 photo of Armstrongite associated with Thorite | Th(SiO4) |
Related Minerals - Strunz-mindat Grouping
| 9.EA. | Hydroxymcglassonite-(K) | KSr4Si8O20(OH) · 8H2O |
| 9.EA. | Miyawakiite-(Y) | ◻Y4Fe2(Si8O20)(CO3)4(H2O)3 |
| 9.EA. | Bussyite-(Y) | (Y,REE,Ca)3(Na,Ca)6MnSi9Be5(O,OH,F)34 |
| 9.EA. | Fluorapophyllite-(NH4) | NH4Ca4(Si8O20)F · 8H2O |
| 9.EA.05 | Gillespite | BaFe2+Si4O10 |
| 9.EA.05 | Cuprorivaite | CaCuSi4O10 |
| 9.EA.05 | Wesselsite | SrCuSi4O10 |
| 9.EA.05 | Effenbergerite | BaCuSi4O10 |
| 9.EA.07 | Fluorapophyllite-(Cs) | CsCa4(Si8O20)F · 8H2O |
| 9.EA.10 | Ekanite | Ca2ThSi8O20 |
| 9.EA.15 | Fluorapophyllite-(Na) | NaCa4(Si8O20)F · 8H2O |
| 9.EA.15 | Fluorapophyllite-(K) | KCa4(Si8O20)(F,OH) · 8H2O |
| 9.EA.15 | Hydroxyapophyllite-(K) | KCa4(Si8O20)(OH,F) · 8H2O |
| 9.EA.20 | Magadiite | Na2Si14O29 · 11H2O |
| 9.EA.25 | Dalyite | K2ZrSi6O15 |
| 9.EA.25 | Davanite | K2TiSi6O15 |
| 9.EA.30 | Sazhinite-(La) | Na3La[Si6O15] · 2H2O |
| 9.EA.30 | Sazhinite-(Ce) | Na3CeSi6O15 · 2H2O |
| 9.EA.40 | Okenite | Ca10Si18O46 · 18H2O |
| 9.EA.45 | Perettiite-(Y) | Y2Mn4FeSi2B8O24 |
| 9.EA.45 | Nekoite | Ca3Si6O15 · 7H2O |
| 9.EA.45 | Badakhshanite-(Y) | Y2Mn4Al(Si2B7BeO24) |
| 9.EA.47 | Shlykovite | KCa[Si4O9(OH)] · 3H2O |
| 9.EA.50 | Diegogattaite | Na2CaCu2Si8O20 · H2O |
| 9.EA.50 | Cavansite | Ca(VO)Si4O10 · 4H2O |
| 9.EA.52 | Yangite | PbMnSi3O8 · H2O |
| 9.EA.55 | Pentagonite | Ca(VO)Si4O10 · 4H2O |
| 9.EA.60 | Penkvilksite | Na4Ti2Si8O22 · 4H2O |
| 9.EA.60 | Tumchaite | Na2Zr(Si4O11) · 2H2O |
| 9.EA.65 | Nabesite | Na2BeSi4O10 · 4H2O |
| 9.EA.70 | Ajoite | (K,Na)Cu7AlSi9O24(OH)6 · 3H2O |
| 9.EA.75 | Zeravshanite | Na2Cs4Zr3[Si18O45]*2H2O |
| 9.EA.80 | Bussyite-(Ce) | (Ce,REE)3(Na,H2O)6MnSi9Be5(O,OH)30F4 |
| 9.EA.85 | Plumbophyllite | Pb2Si4O10 · H2O |
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 Armstrongite
mindat.org URL:
https://www.mindat.org/min-344.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Armstrongite
Reference List:
Jambor, John L.; Roberts, Andrew C.; Grice, Joel D. (1987) Armstrongite from the Strange Lake Alkalic Complex, on the Quebec – Labrador Boundary, Canada. Powder Diffraction, 2 (1). 2-4 doi:10.1017/s0885715600012148
Pushcharovsky, D.Yu., Kabalov, K., Zubkova, N.V., Schneider, J., Sapozhnikov, A.N. (2000) Powder Rietveld refinement of armstrongite, CaZr[Si6O15]·3H2O. Zeitschrift für Kristallographie, 215 (12). 757-761 doi:10.1524/zkri.2000.215.12.757
Mesto, E., Kaneva, E., Schingaro, E., Vladykin, N., Lacalamita, M., Scordari, F. (2014) Armstrongite from Khan Bogdo (Mongolia): Crystal structure determination and implications for zeolite-like cation exchange properties. American Mineralogist, 99 (11) 2424-2432 doi:10.2138/am-2014-4906
Taroev, Vladimir K., Kashaev, Anvar A., Malcherek, Thomas, Goettlicher, Joerg, Kaneva, Ekaterina V., Vasiljev, Alexander D., Suvorova, Ludmila F., Suvorova, Daria S., Tauson, Vladimir L. (2015) Crystal structures of new potassium silicates and aluminosilicates of Sm, Tb, Gd, and Yb and their relation to the armstrongite (CaZr(Si6O15)·3H2O) structure. Journal of Solid State Chemistry, 227. 196-203 doi:10.1016/j.jssc.2015.03.004
Localities for Armstrongite
Showing 10 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.
Australia | |
| www.australianrareearths.com (n.d.) |
| Johns-Mead et al. (2024) |
Canada | |
| Mineralogical Society of America - ... |
| Matte et al. (2025) |
| Jambor et al. (1987) +4 other references | |
Greece | |
| Kapsiotis et al. (2016) |
Mongolia | |
| Kynicky et al. (2018) |
| Kempe et al. (1999) |
| J Kynický et al. (2009) +3 other references |
| Vladykin N.V. et al. (1981) |
Quick NavTopAbout ArmstrongiteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Dorozhnyi pegmatite, Khan Bogd Peralkaline Granite, Khanbogd District, Ömnögovi Province, Mongolia