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Malladrite
A valid IMA mineral species - grandfathered
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About Malladrite
Alessandro Malladra
Formula:
Na2[SiF6]
Colour:
Pale rose, colorless, white
Lustre:
Vitreous, Greasy
Hardness:
3
Specific Gravity:
2.714
Crystal System:
Trigonal
Name:
Named in honor of Alessandro Malladra (1865, Turin, Italy - 1945, Rome, Italy), professor at the College Mellerio Rosmini-Domodossola; director (1927–1935) of the Vesuvius Observatory. He made scientific descents into Vesuvius that were reported on around the world.
Serafimova et al. (1996) report it from a fumarole with wall temperatures of 60 C and gas temperatures of 100 C. AT other times, with higher temperatures, less malladrite was found.
Unique Identifiers
Mindat ID:
2554
Long-form identifier:
mindat:1:1:2554:2
Similar Names
| Mallardite | A valid IMA mineral species - grandfathered | Mn2+(H2O)6(SO4) · H2O |
IMA Classification of Malladrite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Na2SiF6
Classification of Malladrite
3.CH.05
3 : HALIDES
C : Complex halides
H : Silicofluorides
3 : HALIDES
C : Complex halides
H : Silicofluorides
11.5.2.1
11 : HALIDE COMPLEXES
5 : AmBX6
11 : HALIDE COMPLEXES
5 : AmBX6
8.12.3
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
12 : Fluorborates (BF'4) and fluosilicates (SiF''6)
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
12 : Fluorborates (BF'4) and fluosilicates (SiF''6)
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 |
|---|---|---|
| Mld | 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 Malladrite
Vitreous, Greasy
Transparency:
Translucent
Colour:
Pale rose, colorless, white
Hardness:
3 on Mohs scale
Hardness:
VHN10=78 - 84 kg/mm2 - Vickers
Comment:
VHN measured on (0001)
Cleavage:
Perfect
{0001}
{0001}
Density:
2.714 g/cm3 (Measured) 2.756 g/cm3 (Calculated)
Comment:
Calculated by Serafimova et al. 1996
Optical Data of Malladrite
Type:
Uniaxial (-)
RI values:
nω = 1.313 nε = 1.309
Birefringence:
weak
Max. Birefringence:
δ = 0.004
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:
Very High (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 Malladrite
Mindat Formula:
Na2[SiF6]
Element Weights:
Elements listed:
Crystallography of Malladrite
Crystal System:
Trigonal
Class (H-M):
32 - Trapezohedral
Space Group:
P321
Cell Parameters:
a = 8.86 Å, c = 5.04 Å
Ratio:
a:c = 1 : 0.569
Unit Cell V:
342.63 ų (Calculated from Unit Cell)
Morphology:
Crystals prismatic [0001] with basal plane and pyramid.
Tablets showing {0001}, {1120}, and {1010} (Serafimova et al. 1996)
Tablets showing {0001}, {1120}, and {1010} (Serafimova et al. 1996)
Comment:
synthetic
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
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View
CIF File Best | x | y | z | a | b | c
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Rotation
Stop | Start
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Labels
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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) |
|---|---|---|---|---|---|---|---|
| 0009291 | Malladrite | Zalkin A, Forrester J D, Templeton D H (1964) The crystal structure of sodium fluorosilicate Acta Crystallographica 17 1408-1412 |  | 1964 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.426 Å | (67) |
| 4.210 Å | (70) |
| 3.325 Å | (80) |
| 3.053 Å | (67) |
| 2.281 Å | (100) |
| 1.795 Å | (78) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 45b : [Other oxidized fumarolic minerals] | |
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 50 : Coal and/or oil shale minerals | <0.36 |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 54 : Coal and other mine fire minerals (see also #51 and #56) |
Type Occurrence of Malladrite
Place of Conservation of Type Material:
University of Florence, Florence, Italy, 226/l.
Geological Setting of Type Material:
Lava deposits on an active volcano.
Associated Minerals at Type Locality:
Other Language Names for Malladrite
Common Associates
Associations Based on Photo Data:
| 7 photos of Malladrite associated with Avogadrite | (K,Cs)[BF4] |
Related Minerals - Strunz-mindat Grouping
| 3.CH.10 | Bararite | (NH4)2[SiF6] |
| 3.CH.15 | Hieratite | K2[SiF6] |
| 3.CH.15 | Cryptohalite | (NH4)2[SiF6] |
| 3.CH.20 | Demartinite | K2[SiF6] |
| 3.CH.25 | Knasibfite | K3Na4[SiF6]3[BF4] |
| 3.CH.30 | Heklaite | KNaSiF6 |
Other Information
Notes:
Slightly soluble in cold water; slightly more so in hot water.
Solubility 5.7, 9.9, and 24.6 g/L at 15, 40, and 100 C.
Solubility 5.7, 9.9, and 24.6 g/L at 15, 40, and 100 C.
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 Malladrite
mindat.org URL:
https://www.mindat.org/min-2554.html
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Please feel free to link to this page.
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References for Malladrite
Localities for Malladrite
Showing 8 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.
Antarctica | |
| Kammerer (2011) |
Iceland | |
| Garavelli et al. (2010) |
Italy | |
| Russo et al. (2004) |
| Accad.Lincei.Rend.Cl.Sci.fis.mat.nat. (1926) +2 other references |
| Russo et al. (2004) | |
| GARAVELLI A. et al. (1997) |
Poland | |
| Kruszewski (2012) |
Russia | |
| Serafimova et al. (1996) +1 other reference |
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Tolbachik Volcanic field, Milkovsky District, Kamchatka Krai, Russia