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Montesommaite

A valid IMA mineral species
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04954130017271925131951.jpg
Montesommaite

Mount Somma, Metropolitan City of Naples, Campania, Italy
07983690017271925174419.jpg
Montesommaite

San Vito Quarry, San Vito, Ercolano, Metropolitan City of Naples, Campania, Italy
06528360017271925207214.jpg
Montesommaite

Pollena quarries, Pollena Trocchia, Metropolitan City of Naples, Campania, Italy
06639990017271925246343.jpg
Montesommaite

Pollena quarries, Pollena Trocchia, Metropolitan City of Naples, Campania, Italy
04954130017271925131951.jpg
Montesommaite

Mount Somma, Metropolitan City of Naples, Campania, Italy
07983690017271925174419.jpg
Montesommaite

San Vito Quarry, San Vito, Ercolano, Metropolitan City of Naples, Campania, Italy
06528360017271925207214.jpg
Montesommaite

Pollena quarries, Pollena Trocchia, Metropolitan City of Naples, Campania, Italy
06639990017271925246343.jpg
Montesommaite

Pollena quarries, Pollena Trocchia, Metropolitan City of Naples, Campania, Italy
06411330017271925284712.jpg
Montesommaite

Mount Somma, Metropolitan City of Naples, Campania, Italy
03337420017271925314444.jpg
Montesommaite

San Vito Quarry, San Vito, Ercolano, Metropolitan City of Naples, Campania, Italy
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About MontesommaiteHide

05595750017271925278724.jpg
Monte Somma

Mount Somma, Metropolitan City of Naples, Campania, Italy
Formula:
(K,Na)9Al9Si23O64 · 10H2O
Colour:
Colorless
Lustre:
Vitreous
Specific Gravity:
2.34
Crystal System:
Orthorhombic
Member of:
Zeolite Group
Name:
Named in 1990 by Roland C. Rouse, Pete J. Dunn, Joel D. Grice, John L. Sclenker, and John B. Higgins after the type locality of Monte Somma, "the high ridge that constitutes the remains of the volcanic cone that preceded Vesuvius".
Zeolite Group.


Unique IdentifiersHide

Mindat ID:
2766
Long-form identifier:
mindat:1:1:2766:9

IMA Classification of MontesommaiteHide

Classification of MontesommaiteHide

Strunz-mindat (2025):
9.GB.30

9 : SILICATES (Germanates)
G : Tektosilicates with zeolitic H2O; zeolite family
B : Chains of single connected 4-membered rings
Dana 8th ed.:
77.1.3.12

77 : TECTOSILICATES Zeolites
1 : Zeolite group - True zeolites
Hey's CIM Ref.:
16.4.6

16 : Silicates Containing Aluminum and other Metals
4 : Aluminosilicates of Na and K

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference
MtsoIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of MontesommaiteHide

Lustre:
Vitreous
Transparency:
Transparent
Colour:
Colorless
Streak:
White
Hardness Data:
Could not be measured
Cleavage:
None Observed
Density:
2.34(4) g/cm3 (Measured)    2.30 g/cm3 (Calculated)

Optical Data of MontesommaiteHide

Type:
Biaxial (-)
RI values:
nα = 1.498(1) nβ = 1.506(1) nγ = 1.507(1)
2V:
Measured: 35° (5), Calculated: 38°
Max. Birefringence:
δ = 0.009
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.

Surface Relief:
Moderate
Dispersion:
very weak
Optical Extinction:
X = c, Y = a or b, and Z = a or b

Chemistry of MontesommaiteHide

Mindat Formula:
(K,Na)9Al9Si23O64 · 10H2O
Element Weights:
Element% weight
O48.428 %
Si26.422 %
K14.393 %
Al9.933 %
H0.825 %

Calculated from ideal end-member formula.
Elements listed:
Al, H, K, Na, O, Si - search for minerals with similar chemistry

Crystallography of MontesommaiteHide

Crystal System:
Orthorhombic
Class (H-M):
mm2 - Pyramidal
Space Group:
Fdd2
Cell Parameters:
a = 10.099(1) Å, b = 10.099(1) Å, c = 17.307(3) Å
Ratio:
a:b:c = 1 : 1 : 1.714
Unit Cell V:
1,765.14 ų (Calculated from Unit Cell)
Morphology:
Type material: Two pedions {001} and {001} and two pyramids {hkl} and {hkl}.

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0001338MontesommaiteRouse R C, Dunn P J, Grice J D, Schlenker J L, Higgins J B (1990) Montesommaite, (K,Na)9Al9Si23O64.10H2O, a new zeolite related to merlinoite and the gismondine group American Mineralogist 75 1415-142019900293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
6.589 Å(75)
4.334 Å(43)
3.299 Å(100)
3.130 Å(100)
2.797 Å(30)
2.513 Å(18)
2.347 Å(22)
1.784 Å(22)
1.720 Å(16)
1.558 Å(18)

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 3a: Earth’s earliest Hadean crust>4.50
9 : Lava/xenolith minerals (hornfels, sanidinite facies)
10 : Basalt-hosted zeolite minerals

Type Occurrence of MontesommaiteHide

Type Locality:
ⓘ Pollena quarries, Pollena Trocchia, Metropolitan City of Naples, Campania, Italy
General Appearance of Type Material:
Transparent, colorless, euhedral crystals up to 0.1 mm in size.
Place of Conservation of Type Material:
National Museum of Natural History, Washington, D.C., USA, 165440.
Geological Setting of Type Material:
Vesicles in scoria
Associated Minerals at Type Locality:
DolomiteCalciteChabaziteNatrolite
Reference:
Rouse, R.C., Dunn, P.J., Grice, J.D., Schlenker, J.L., Higgins, J.B. (1990) Montesommaite, (K,Na)9Al9Si23O64·10H2O, a new zeolite related to merlinoite and the gismondine group. American Mineralogist: 75: 1415-1420.

Synonyms of MontesommaiteHide

Other Language Names for MontesommaiteHide

Relationship of Montesommaite to other SpeciesHide

Member of:
Zeolite Group
Other Members of Zeolite Group:
AlflarseniteNaCa2Be3Si4O13(OH) · 2H2OMon. 2 : P21
AmiciteK2Na2Al4Si4O16 · 5H2OMon. 2
Ammonioleucite(NH4)(AlSi2O6)Tet. 4/m : I41/a
AnalcimeNa(AlSi2O6) · H2OTric. 1 : P1
ArzamastseviteK6Al5Si6O20(OH)4ClTet. 4 2m : I4 2m
Bellbergite(K,Ba,Sr)2Sr2Ca2(Ca,Na)4[Al3Si3O12]6 · 30H2OHex.
BikitaiteLiAlSi2O6 · H2OTric. 1 : P1
BoggsiteCa8Na3(Si,Al)96O192 · 70H2OOrth. mmm (2/m 2/m 2/m) : Imma
Brewsterite SubgroupZeolite Group.
Chabazite-Levyne SubgroupM[Al2Si4O12] · 6H2O
ChiavenniteCaMnBe2Si5O13(OH)2 · 2H2OMon. 2/m : P21/b
Clinoptilolite Subgroup(Na/Ca/K)3-6[Al6-7Si29-30O72] · 20H2O
CowlesiteCaAl2Si3O10 · 6H2OOrth. mmm (2/m 2/m 2/m)
Dachiardite SubgroupZeolite Group.
DirenzoiteNaK6MgCa2(Al13Si47O120) · 36H2OOrth. mmm (2/m 2/m 2/m) : Pmmn
EdingtoniteBa[Al2Si3O10] · 4H2OOrth. 2 2 2 : P21 21 21
EpistilbiteCaAl2Si6O16 · 5H2OMon.
Erionite SubgroupM2[Al4Si14O36] · 15H2O
FabrièsiteNa3Al3Si3O12 · 2H2OOrth. mm2 : Pmm2
Faujasite SubgroupM3.5[Al7Si17O48] · 32H2O
Ferrierite SubgroupName used for unanalysed specimens that could be either ferrierite-K, ferrierite-Mg, ...
FerrochiavenniteCa1-2Fe[(Si,Al,Be)5Be2O13(OH)2] · 2H2OMon. 2/m : P21/b
Flörkeite(K3Ca2Na)[Al8Si8O32] · 12H2OTric. 1 : P1
Garronite Subgroup
GaultiteNa4Zn2Si7O18 · 5H2OOrth. mm2 : Fdd2
Gismondine SubgroupZeolite Group.
Gmelinite SubgroupIn 1997, gmelinite was split into Gmelinite-Ca, Gmelinite-Na and Gmelinite-K.
GobbinsiteNa5(Si11Al5)O32 · 11H2OOrth. mmm (2/m 2/m 2/m) : Pnma
GoosecreekiteCa[Al2Si6O16] · 5H2OMon. 2 : P21
GottardiiteNa3Mg3Ca5Al19Si117O272 · 93H2OOrth. mmm (2/m 2/m 2/m) : Cmca
Heulandite Subgroup(Na/Ca/K)5-6[Al8-9 Si27-28 O72] · nH2O
HsianghualiteCa3Li2(Be3Si3O12)F2Iso. 4 3 2 : I41 3 2
KalborsiteK6Al4BSi6O20(OH)4ClTet. 4 2m : P4 21c
KirchhoffiteCs(BSi2O6)Tet. 4/mmm (4/m 2/m 2/m) : I41/acd
LaumontiteCaAl2Si4O12 · 4H2OMon. 2/m : B2/m
LeuciteK(AlSi2O6)Tet. 4/m : I41/a
LimousiniteBaCa[Be4P4O16] · 6H2OMon. 2/m : P21/b
LithositeK6Al4Si8O25 · 2H2OMon.
Loomisite Ba[Be2P2O8] · H2OMon. m
LovdariteK2Na6Be4Si14O36 · 9H2OOrth. mm2
MaricopaitePb7Ca2(Si,Al)48O100 · 32H2OOrth.
MartinandresiteBa2(Al4Si12O32) · 10H2OOrth. mmm (2/m 2/m 2/m) : Pmmn
Mazzite SubgroupZeolite Group.
MeieriteBa44Si66Al30O192Cl25(OH)33Iso. m3m (4/m 3 2/m) : Im3m
MerlinoiteK5Ca2(Si23Al9)O64 · 24H2OOrth. mmm (2/m 2/m 2/m) : Immm
Mordenite(Na2,Ca,K2)4(Al8Si40)O96 · 28H2OOrth.
MountainiteKNa2Ca2[Si8O19(OH)] · 6H2OMon. 2/m : P2/b
MutinaiteNa3Ca4Si85Al11O192 · 60H2OOrth. mmm (2/m 2/m 2/m) : Pnma
NabesiteNa2BeSi4O10 · 4H2OOrth. 2 2 2 : P21 21 21
Natrolite SubgroupA subgroup of the Zeolite Group.
OffretiteKCaMg(Si13Al5)O36 · 15H2OHex. 6 m2 : P6m2
PahasapaiteLi8(Ca,Li,K)10.5Be24(PO4)24 · 38H2OIso. 2 3 : I2 3
ParthéiteCa2(Si4Al4) O15 (OH)2 · 4H2OMon. 2/m : B2/b
Paulingite SubgroupPaulingite was originally described in 1960.
PerlialiteK9Na(Ca,Sr)[Al2Si4O12]6 · 15H2OHex. 6/mmm (6/m 2/m 2/m) : P6/mmm
Phillipsite Subgroup(Ca0.5,K,Na,Ba0.5)4-7[Al4-7Si12-9O32] . 12H2O
Pollucite(Cs,Na)2(Al2Si4O12) · 2H2OIso. m3m (4/m 3 2/m) : Ia3d
RoggianiteCa2Be(OH)2Al2Si4O13 · 2.5H2OTet. 4/mmm (4/m 2/m 2/m) : I4/mcm
RongibbsitePb2(Si4Al)O11(OH) Mon. 2/m : B2/m
Stilbite SubgroupM6-7[Al8-9Si27-28O72] · nH2O
Terranovaite(Na,Ca)8(Si68Al12)O160 · 29H2OOrth.
Thomsonite SubgroupThe large majority of "thomsonite" is thomsonite-Ca.
Thornasite(Na,K)12Th3[Si8O19]4 · 18H2OTrig. 3m : R3m
Tschernichite(Ca,Na2)[Al2Si4O12] · 4-8H2OTet. 4/mmm (4/m 2/m 2/m) : P4/mmm
TschörtneriteCa4(Ca,Sr,K,Ba)3Cu3[Al3Si3O12]4(OH)8 · nH2OIso. m3m (4/m 3 2/m) : Fm3m
UM1996-38-SiO:AlCaHNaNa-Ca-Al-Si-O-H
UM1999-33-SiO:AlHKNaK7Na5Al12Si20O64 · 24H2O
UM2002-40-SiO:AlCaHKMgNa(Mg,Ca,Na,K)7.5(Al12.8Si51.2)O128 · 65H2OTet. 4 2 2 : P41 2 2
Unnamed (Ca analogue of Merlinoite)(Ca,K,Na)5(Ca,Ba)2Al9Si23O64 · 23H2O ?
WairakiteCa(Al2Si4O12) · 2H2OMon. 2/m : B2/m
WeinebeneiteCaBe3(PO4)2(OH)2 · 4H2OMon. m : Bb
Wenkite(Ba,K)4(Ca,Na)6[(Si,Al)20O39(OH)2](SO4)3 · 0.5H2OHex. 6 m2 : P62m
Wilancookite(Ba5Li2◻)Ba6Be24P24O96 · 26H2OIso. 2 3 : I2 3
WillhendersoniteKCa[Al3Si3O12] · 5H2OTric. 1 : P1
YugawaraliteCaAl2Si6O16 · 4H2OMon. m : Pb

Common AssociatesHide

Associated Minerals Based on Photo Data:
5 photos of Montesommaite associated with MerlinoiteK5Ca2(Si23Al9)O64 · 24H2O
3 photos of Montesommaite associated with Phillipsite-KK6(Si10Al6)O32 · 12H2O
2 photos of Montesommaite associated with CalciteCaCO3

Related Minerals - Strunz-mindat GroupingHide

9.GB.05FabrièsiteNa3Al3Si3O12 · 2H2OOrth. mm2 : Pmm2
9.GB.05LithositeK6Al4Si8O25 · 2H2OMon.
9.GB.05WairakiteCa(Al2Si4O12) · 2H2OMon. 2/m : B2/m
9.GB.05KirchhoffiteCs(BSi2O6)Tet. 4/mmm (4/m 2/m 2/m) : I41/acd
9.GB.05HsianghualiteCa3Li2(Be3Si3O12)F2Iso. 4 3 2 : I41 3 2
9.GB.05LeuciteK(AlSi2O6)Tet. 4/m : I41/a
9.GB.05Pollucite(Cs,Na)2(Al2Si4O12) · 2H2OIso. m3m (4/m 3 2/m) : Ia3d
9.GB.05Ammonioleucite(NH4)(AlSi2O6)Tet. 4/m : I41/a
9.GB.05AnalcimeNa(AlSi2O6) · H2OTric. 1 : P1
9.GB.10LaumontiteCaAl2Si4O12 · 4H2OMon. 2/m : B2/m
9.GB.15YugawaraliteCaAl2Si6O16 · 4H2OMon. m : Pb
9.GB.20RoggianiteCa2Be(OH)2Al2Si4O13 · 2.5H2OTet. 4/mmm (4/m 2/m 2/m) : I4/mcm
9.GB.25GoosecreekiteCa[Al2Si6O16] · 5H2OMon. 2 : P21
9.GB.35ParthéiteCa2(Si4Al4) O15 (OH)2 · 4H2OMon. 2/m : B2/b

RadioactivityHide

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) 14.3932% 4,462 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: –

DistanceDose rateRisk
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

Fluorescence of MontesommaiteHide

In UV light:
No fluorescence with LW or SW UV

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.

Internet Links for MontesommaiteHide

References for MontesommaiteHide

Localities for MontesommaiteHide

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 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). 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 (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
Italy
 
  • Campania
    • Metropolitan City of Naples
      • Ercolano
        • San Vito
Ciriotti et al. (2004)
      • Pollena Trocchia
Rouse et al. (1990)
      • Sant'Anastasia
Bortolozzi (n.d.) +1 other reference
      • Somma Vesuviana
Russo (1996)
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