Demartinite
A valid IMA mineral species
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About Demartinite
Francesco Demartin
Formula:
K2[SiF6]
Colour:
Colorless
Specific Gravity:
2.85
Crystal System:
Hexagonal
Name:
After Francesco Demartin (born 1953), professor of General and Inorganic Chemistry and Stechiometry at the University of Milan, Italy. He has made significant contributions to the chemistry of metallic clusters in organometallic compounds and to the crystal structure of Alpine rare-earth minerals and uranium minerals.
Type Locality:
Dimorph of:
This page provides mineralogical data about Demartinite.
Unique Identifiers
Mindat ID:
30908
Long-form identifier:
mindat:1:1:30908:6
IMA Classification of Demartinite
Classification of Demartinite
3.CH.20
3 : HALIDES
C : Complex halides
H : Silicofluorides
3 : HALIDES
C : Complex halides
H : Silicofluorides
11.5.2.3
11 : HALIDE COMPLEXES
5 : AmBX6
11 : HALIDE COMPLEXES
5 : AmBX6
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 |
|---|---|---|
| Dma | 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 Demartinite
Transparency:
Transparent
Colour:
Colorless
Streak:
White
Density:
2.85 g/cm3 (Measured) 2.87 g/cm3 (Calculated)
Optical Data of Demartinite
Type:
Uniaxial (-)
RI values:
nω = 1.350(5) nε = 1.340(5)
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
Pleochroism:
Non-pleochroic
Chemistry of Demartinite
Mindat Formula:
K2[SiF6]
Element Weights:
Elements listed:
Crystallography of Demartinite
Crystal System:
Hexagonal
Class (H-M):
6mm - Dihexagonal Pyramidal
Space Group:
P63mc
Cell Parameters:
a = 5.6461(8) Å, c = 9.2322(18) Å
Ratio:
a:c = 1 : 1.635
Unit Cell V:
254.88 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Hexagonal pyramidal crystals. The observed forms are the pedion {001} and the hexagonal pyramid {112}.
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
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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) |
|---|---|---|---|---|---|---|---|
| 0006157 | Demartinite | Gramaccioli C M, Campostrini I (2007) Demartinite, a new polymorph of K2SiF6 from La Fossa Crater, Vulcano, Aeolian Islands, Italy The Canadian Mineralogist 45 1275-1280 |  | 2007 | La Fossa Crater, Vulcano Island, Aeolian Archipelago, Sicily, Italy | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.90 Å | (25) |
| 4.62 Å | (75) |
| 4.32 Å | (43) |
| 2.358 Å | (22) |
| 2.301 Å | (100) |
| 2.155 Å | (54) |
| 1.909 Å | (14) |
| 1.403 Å | (13) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 45b : [Other oxidized fumarolic minerals] |
Type Occurrence of Demartinite
General Appearance of Type Material:
Colorless hexagonal pyramidal crystals up to 0.3 mm across.
Place of Conservation of Type Material:
State University of Milan, Italy, number 2006-1.
Geological Setting of Type Material:
From a fumarole, on a fragment of altered pyroclastic breccia.
Associated Minerals at Type Locality:
Synonyms of Demartinite
Other Language Names for Demartinite
Dutch:Demartiniet
German:Demartinit
Common Associates
Associations Based on Photo Data:
| 3 photos of Demartinite associated with Hieratite | K2[SiF6] |
| 1 photo of Demartinite associated with Knasibfite | K3Na4[SiF6]3[BF4] |
| 1 photo of Demartinite associated with Native Sulphur | S8 |
Related Minerals - Strunz-mindat Grouping
| 3.CH.05 | Malladrite | Na2[SiF6] |
| 3.CH.10 | Bararite | (NH4)2[SiF6] |
| 3.CH.15 | Hieratite | K2[SiF6] |
| 3.CH.15 | Cryptohalite | (NH4)2[SiF6] |
| 3.CH.25 | Knasibfite | K3Na4[SiF6]3[BF4] |
| 3.CH.30 | Heklaite | KNaSiF6 |
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) | 35.4999% | 11,005 | 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
Notes:
Not hygroscopic.
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 Demartinite
mindat.org URL:
https://www.mindat.org/min-30908.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Demartinite
Reference List:
Denaeyer, Marcel E., Ledent, D. (1952) Sur la présence de la modification hexagonale de la hiératite (camermanite) dans des incrustations de sels potassiques d'une cheminée d'usine. Bulletin de Minéralogie, 75 (4) 231-236 doi:10.3406/bulmi.1952.4772
Localities for Demartinite
Showing 2 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.
Italy (TL) | |
| Gramaccioli et al. (2007) |
Russia | |
| Zelenski et al. (2020) |
Quick NavTopAbout DemartiniteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatRadioactivityOther InformationInternet Links References Localities Locality List
Vulcano Island, Lipari, Eolie Islands, Metropolitan City of Messina, Sicily, Italy