Microsommite
A valid IMA mineral species - grandfathered
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About Microsommite
Formula:
Na4K2Ca2(Al6Si6O24)(SO4)Cl2
Colour:
colourless, white
Lustre:
Silky
Hardness:
6
Specific Gravity:
2.42 - 2.53
Crystal System:
Hexagonal
Member of:
Name:
Named in 1872 by A. Scacchi. Name derived from 'micro' for the small crystal size and the type locality of Monte Somma, Italy.
Unique Identifiers
Mindat ID:
2706
Long-form identifier:
mindat:1:1:2706:5
IMA Classification of Microsommite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
[(Na,K)6(S6+O4)][Ca2Cl2][(Si6Al6O24)]
Classification of Microsommite
9.FB.05
9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
B : Tektosilicates with additional anions
9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H2O
B : Tektosilicates with additional anions
76.2.5.10
76 : TECTOSILICATES Al-Si Framework
2 : Al-Si Framework Feldspathoids and related species
76 : TECTOSILICATES Al-Si Framework
2 : Al-Si Framework Feldspathoids and related species
17.10.8
17 : Silicates Containing other Anions
10 : Silicates with sulphate, molybdate or tungstate
17 : Silicates Containing other Anions
10 : Silicates with sulphate, molybdate or tungstate
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 |
|---|---|---|
| Msm | 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 Microsommite
Silky
Transparency:
Transparent
Comment:
Silky to brilliant on {1010}
Colour:
Colourless, white
Streak:
White
Hardness:
6 on Mohs scale
Cleavage:
Perfect
{1010}, perfect; {0001}, less distinct
{1010}, perfect; {0001}, less distinct
Density:
2.42 - 2.53 g/cm3 (Measured) 2.48 g/cm3 (Calculated)
Optical Data of Microsommite
Type:
Uniaxial (+)
RI values:
nω = 1.521 nε = 1.529
Max. Birefringence:
δ = 0.008
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 uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Chemistry of Microsommite
Mindat Formula:
Na4K2Ca2(Al6Si6O24)(SO4)Cl2
Element Weights:
Crystallography of Microsommite
Crystal System:
Hexagonal
Class (H-M):
622 - Trapezohedral
Space Group:
P6322
Cell Parameters:
a = 22.08(4) Å, c = 5.33(2) Å
Ratio:
a:c = 1 : 0.241
Unit Cell V:
2,250.38 ų (Calculated from Unit Cell)
Z:
3
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) |
|---|---|---|---|---|---|---|---|
| 0008599 | Microsommite | Bonaccorsi E, Merlino S, Pasero M, Macedonio G (2001) Microsommite: crystal chemistry, phase transitions, Ising model and Monte Carlo simulations Physics and Chemistry of Minerals 28 509-522 | 2001 | 0 | 293 | ||
| 0007926 | Microsommite | Bonaccorsi E, Comodi P, Merlino S (1995) Thermal behaviour of davyne-group minerals Physics and Chemistry of Minerals 22 367-374 | 1995 | 0 | 293 | ||
| 0007925 | Microsommite | Bonaccorsi E, Comodi P, Merlino S (1995) Thermal behaviour of davyne-group minerals Physics and Chemistry of Minerals 22 367-374 | 1995 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.81 Å | (100) |
| 3.69 Å | (100) |
| 3.29 Å | (100) |
| 2.670 Å | (80) |
| 2.660 Å | (80) |
| 2.765 Å | (60) |
| 2.455 Å | (60) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 31 : Thermally altered carbonate, phosphate, and iron formations | |
| Stage 4b: Highly evolved igneous rocks | >3.0 |
| 35 : Ultra-alkali and agpaitic igneous rocks |
Type Occurrence of Microsommite
Place of Conservation of Type Material:
Natural History Museum, Paris, France, 97397
Geological Setting of Type Material:
ejected volcanic masses and in leucitites.
Associated Minerals at Type Locality:
Synonyms of Microsommite
Other Language Names for Microsommite
Relationship of Microsommite to other Species
Member of:
Other Members of Cancrinite Group:
| Afghanite | (Na,K)22Ca10(Si24Al24O96)(SO4)6Cl6 | Trig. 3m : P31c |
| Alloriite | (Na,Ca,K)26Ca4(Al6Si6O24)4(SO4)6Cl6 | Trig. 3m : P31c |
| Balliranoite | (Na,K)6Ca2(Si6Al6O24)Cl2(CO3) | Hex. 6 : P63 |
| Betzite | Na6Ca2(Al6Si6O24)Cl4 | Hex. 6 : P63 |
| Biachellaite | (Na,Ca,K)8(Al6Si6O24)(SO4)2(OH)0.5 · H2O | Trig. 3 : P3 |
| Bystrite | (Na,K)7Ca(Al6Si6O24)(S5)Cl | Trig. 3m : P31c |
| Cancrinite | (Na,Ca,◻)8(Al6Si6O24)(CO3,SO4)2 · 2H2O | Hex. 6 : P63 |
| Cancrisilite | Na7(Al5Si7O24)(CO3) · 3H2O | Hex. 6mm : P63mc |
| Carbobystrite | Na8(Al6Si6O24)(CO3) · 3.5H2O | Trig. 3m : P31c |
| Davyne | (Na,K)6Ca2(Al6Si6O24)(Cl2,SO4)2 | Hex. 6/m : P63/m |
| Depmeierite | Na8(Al6Si6O24)(PO4,CO3)1-x · 3H2O (x<0.5) | Hex. 6 : P63 |
| Fantappièite | [Na82.5Ca33K16.5](Si99Al99O396)(SO4)33 · 4H2O | Trig. 3 : R3 |
| Farneseite | (Na,Ca,K)56(Al6Si6O24)7(SO4)12 · 6H2O | Hex. 6/m : P63/m |
| Franzinite | (Na,K)6Ca2(Al6Si6O24)(SO4)2 · 0.5H2O | Hex. |
| Giuseppettite | (Na,K,Ca)7-8(Al6Si6O24)(SO4,Cl)1-2 | Trig. 3m : P31c |
| Hydroxycancrinite | Na8(Al6Si6O24)(OH)2 · 2H2O | Hex. 6 : P63 |
| Kircherite | Na5Ca2K(Al6Si6O24)(SO4)2 · 0.33H2O | Trig. 32 : R32 |
| Kyanoxalite | Na7(Al6-xSi6+xO24)(C2O4)0.5+x · 5H2O (0 < x < 0.5) | Hex. 6 : P63 |
| Liottite | (Na,K)16Ca8(Al6Si6O24)3(SO4)5Cl4 | Hex. 6 : P6 |
| Marinellite | (Na,K)42Ca6(Al6Si6O24)6(SO4)8Cl2 · 3H2O | Trig. 3m : P31c |
| Pitiglianoite | Na6K2(Al6Si6O24)(SO4) · 2H2O | Hex. 6 : P63 |
| Quadridavyne | (Na,K)6Ca2(Al6Si6O24)Cl4 | Hex. 6/m : P63/m |
| Sacrofanite | (Na61K19Ca32)(Si84Al84O336)(SO4)26Cl2F6 · 2H2O | Hex. |
| Steudelite | Na3(K17Ca7)Ca4(Al24Si24O96)(SO3)6F6 · 4H2O | Hex. 6m2 : P62c |
| Sulfhydrylbystrite | Na5K2Ca[Al6Si6O24](S5)2(SH) | Trig. 3m : P31c |
| Tounkite | (Na,Ca,K)8(Si6Al6)O24(SO4)2Cl · 0.5H2O | Hex. 622 : P6222 |
| 'UM2004-48-SiO:AlClCaNaS' | (Na,Ca)8(Si6Al6)O24(SO4)1.7Cl1.3 | |
| 'UM2009-23-SiO:AlCCaClHKNaS' | (Na,Ca)24K10[(Si,Al)60O120](SO4)5.6Cl1.5(CO3)0.4 · 11H2O | Trig. 3 : P3 |
| Vishnevite | (Na,K)8(Al6Si6O24)(SO4,CO3) · 2H2O | Hex. 6 : P63 |
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 9.FB. | Perchukite-(Y) | PbYAsSi2O8 |
| 9.FB. | Åsgruvanite-(Ce) | Ce16Ca5Al(SiO4)6(AsO3)8(CO3)2Cl4F3(OH)2 |
| 9.FB. | Steudelite | Na3(K17Ca7)Ca4(Al24Si24O96)(SO3)6F6 · 4H2O |
| 9.FB. | Wenlanzhangite-(Y) | Y2V3+2V4+2(SiO4)2O4(OH)4 |
| 9.FB. | Slyudyankaite | Na28Ca4(Si24Al24O96)(SO4)6(S6)1/3(CO2) · 2H2O |
| 9.FB. | Bolotinaite | (Na7◻)(Al6Si6O24)F · 4H2O |
| 9.FB. | Sapozhnikovite | Na8(Al6Si6O24)(HS)2 |
| 9.FB. | Betzite | Na6Ca2(Al6Si6O24)Cl4 |
| 9.FB.05 | Quadridavyne | (Na,K)6Ca2(Al6Si6O24)Cl4 |
| 9.FB.05 | Sulfhydrylbystrite | Na5K2Ca[Al6Si6O24](S5)2(SH) |
| 9.FB.05 | Marinellite | (Na,K)42Ca6(Al6Si6O24)6(SO4)8Cl2 · 3H2O |
| 9.FB.05 | Afghanite | (Na,K)22Ca10(Si24Al24O96)(SO4)6Cl6 |
| 9.FB.05 | Bystrite | (Na,K)7Ca(Al6Si6O24)(S5)Cl |
| 9.FB.05 | Franzinite | (Na,K)6Ca2(Al6Si6O24)(SO4)2 · 0.5H2O |
| 9.FB.05 | Kyanoxalite | Na7(Al6-xSi6+xO24)(C2O4)0.5+x · 5H2O (0 < x < 0.5) |
| 9.FB.05 | Vishnevite | (Na,K)8(Al6Si6O24)(SO4,CO3) · 2H2O |
| 9.FB.05 | Farneseite | (Na,Ca,K)56(Al6Si6O24)7(SO4)12 · 6H2O |
| 9.FB.05 | Alloriite | (Na,Ca,K)26Ca4(Al6Si6O24)4(SO4)6Cl6 |
| 9.FB.05 | Liottite | (Na,K)16Ca8(Al6Si6O24)3(SO4)5Cl4 |
| 9.FB.05 | Depmeierite | Na8(Al6Si6O24)(PO4,CO3)1-x · 3H2O (x<0.5) |
| 9.FB.05 | Biachellaite | (Na,Ca,K)8(Al6Si6O24)(SO4)2(OH)0.5 · H2O |
| 9.FB.05 | Cancrinite | (Na,Ca,◻)8(Al6Si6O24)(CO3,SO4)2 · 2H2O |
| 9.FB.05 | Cancrisilite | Na7(Al5Si7O24)(CO3) · 3H2O |
| 9.FB.05 | Fantappièite | [Na82.5Ca33K16.5](Si99Al99O396)(SO4)33 · 4H2O |
| 9.FB.05 | Carbobystrite | Na8(Al6Si6O24)(CO3) · 3.5H2O |
| 9.FB.05 | Pitiglianoite | Na6K2(Al6Si6O24)(SO4) · 2H2O |
| 9.FB.05 | Tounkite | (Na,Ca,K)8(Si6Al6)O24(SO4)2Cl · 0.5H2O |
| 9.FB.05 | Balliranoite | (Na,K)6Ca2(Si6Al6O24)Cl2(CO3) |
| 9.FB.05 | Giuseppettite | (Na,K,Ca)7-8(Al6Si6O24)(SO4,Cl)1-2 |
| 9.FB.05 | Sacrofanite | (Na61K19Ca32)(Si84Al84O336)(SO4)26Cl2F6 · 2H2O |
| 9.FB.05 | Kircherite | Na5Ca2K(Al6Si6O24)(SO4)2 · 0.33H2O |
| 9.FB.05 | Hydroxycancrinite | Na8(Al6Si6O24)(OH)2 · 2H2O |
| 9.FB.05 | Davyne | (Na,K)6Ca2(Al6Si6O24)(Cl2,SO4)2 |
| 9.FB.10 | Haüyne | Na3Ca(Si3Al3)O12(SO4) |
| 9.FB.10 | Lazurite | Na7Ca(Al6Si6O24)(SO4)(S3) · H2O |
| 9.FB.10 | Danalite | Be3Fe2+4(SiO4)3S |
| 9.FB.10 | Helvine | Be3Mn2+4(SiO4)3S |
| 9.FB.10 | Kamaishilite | Ca2(Al2SiO6)(OH)2 |
| 9.FB.10 | Sodalite | Na4(Si3Al3)O12Cl |
| 9.FB.10 | Nosean | Na8(Al6Si6O24)(SO4) · H2O |
| 9.FB.10 | Genthelvite | Be3Zn4(SiO4)3S |
| 9.FB.10 | Bicchulite | Ca2(Al2SiO6)(OH)2 |
| 9.FB.10 | Tsaregorodtsevite | (N(CH3)4)(AlSi5O12) |
| 9.FB.10 | Vladimirivanovite | Na6Ca2(Al6Si6O24)(SO4,S3,S2,Cl)2 · H2O |
| 9.FB.10 | Tugtupite | (BeAlSi)Na4(SiO4)3Cl |
| 9.FB.15 | Marialite | Na4Al3Si9O24Cl |
| 9.FB.15 | Meionite | Ca4Al6Si6O24CO3 |
| 9.FB.15 | Silvialite | (Ca,Na)4(Al6Si6O24)(SO4,CO3) |
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) | 6.9099% | 2,142 | 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 Microsommite
mindat.org URL:
https://www.mindat.org/min-2706.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Microsommite
Reference List:
Bariand, Pierre, Cesbron, Fabien, Giraud, Roger (1968) Une nouvelle espèce minérale : l'afghanite de Sar-e-Sang, Badakhshan, Afghanistan. Comparaison avec les minéraux de groupe de la cancrinite. Bulletin de Minéralogie, 91 (1) 34-42 doi:10.3406/bulmi.1968.6184
Rinaldi, R., Wenk, H. R. (1979) Stacking variations in cancrinite minerals. Acta Crystallographica Section A: Crystal Physics, Diffraction, Theoretical and General Crystallography, 35 (5). 825-828 doi:10.1107/s0567739479001868
Hassan, I., Grundy, H. D. (1984) The crystal structures of sodalite-group minerals. Acta Crystallographica Section B Structural Science, 40 (1) 6-13 doi:10.1107/s0108768184001683
Localities for Microsommite
Showing 11 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.
France | |
| Fermis (2022) |
| Médard P. et al. (2009) |
Italy | |
| Fedele L. et al. (2006) |
| Rath | |
| Mateo Chinelatto photo |
| M. Carati - Guida alla mineralogia ... |
| samples analysed by Dr. Tony Kampf +1 other reference |
| Scacchi (1881) +5 other references |
| Knuever et al. (2023) | |
| Gentile P. (1985) +1 other reference |
Tajikistan | |
| Solovova et al. (2006, October) |
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Pollena quarries, Pollena Trocchia, Metropolitan City of Naples, Campania, Italy