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Chloromagnesite

A valid IMA mineral species - grandfathered - questionable
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Formula:
MgCl2
Colour:
Colourless, white
Specific Gravity:
2.325
Crystal System:
Trigonal
Name:
In allusion to the composition, containing CHLORine and MAGNESium.
Isostructural with:
Lawrencite, Scacchite
Lawrencite Group.

A doubtful species. Natural magnesium chloride is regarded as very unlikely.


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Unique IdentifiersHide

Mindat ID:
1022
Long-form identifier:
mindat:1:1:1022:7

IMA Classification of ChloromagnesiteHide

IMA status:
Approved, 'Grandfathered' (first described prior to 1959), Questionable

Classification of ChloromagnesiteHide

Strunz-mindat (2026):
3.AB.20

3 : HALIDES
A : Simple halides, without H2O
B : M:X = 1:2
Dana 8th ed.:
9.2.3.3

9 : NORMAL HALIDES
2 : AX2

Mineral SymbolsHide

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

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

Physical Properties of ChloromagnesiteHide

Colour:
Colourless, white
Density:
2.325 g/cm3 (Measured)    2.44 g/cm3 (Calculated)

Optical Data of ChloromagnesiteHide

Type:
Uniaxial (-)
RI values:
nω = 1.675 nε = 1.59
Max. Birefringence:
δ = 0.085
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.

Surface Relief:
High (positive)
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.

Chemistry of ChloromagnesiteHide

Mindat Formula:
MgCl2
Element Weights:
Element% weight
Cl74.473 %
Mg25.528 %

Calculated from ideal end-member formula.
Cl
Mg
Elements listed:
Cl, Mg - search for minerals with similar chemistry

Crystallography of ChloromagnesiteHide

Crystal System:
Trigonal
Class (H-M):
3m(32/m) - Hexagonal Scalenohedral
Space Group:
R3m
Setting:
R32/m
Cell Parameters:
a = 3.596 Å, c = 17.589 Å
Ratio:
a:c = 1 : 4.891
Unit Cell V:
196.98 ų (Calculated from Unit Cell)
Morphology:
Sublimate.

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0011808ChloromagnesiteWyckoff R W G (1963) Second edition. Interscience Publishers, New York, New York Crystal Structures 1 239-44419630293
CIF Raw Data - click here to close

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest 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 ChloromagnesiteHide

Synonyms of ChloromagnesiteHide

Other Language Names for ChloromagnesiteHide

Relationship of Chloromagnesite to other SpeciesHide

Member of:
Lawrencite Group
Other Members of Lawrencite Group:
Lawrencite(Fe2+,Ni)Cl2Trig. 3m(32/m) : R3m
ScacchiteMnCl2Trig. 3m(32/m) : R3m
TolbachiteCuCl2Mon. 2/m : B2/m

Related Minerals - Strunz-mindat GroupingHide

3.AB.ManuelarossiitePbCaAlF7Mon. 2/m : B2/m
3.AB.FluorocronitePbF2Iso. m3m(4/m32/m) : Fm3m
3.AB.05TolbachiteCuCl2Mon. 2/m : B2/m
3.AB.10CocciniteHgI2Tet. 4/mmm(4/m2/m2/m) : P42/nmc
3.AB.15SellaiteMgF2Tet. 4/mmm(4/m2/m2/m) : P42/mnm
3.AB.20Lawrencite(Fe2+,Ni)Cl2Trig. 3m(32/m) : R3m
3.AB.20ScacchiteMnCl2Trig. 3m(32/m) : R3m
3.AB.25FluoriteCaF2Iso. m3m(4/m32/m) : Fm3m
3.AB.25FrankdicksoniteBaF2Iso. m3m(4/m32/m) : Fm3m
3.AB.25StrontiofluoriteSrF2Iso. m3m(4/m32/m) : Fm3m
3.AB.30Tveitite-(Y)(Y, Na)6Ca6Ca6(Ca,Na)F42Trig. 3 : R3
3.AB.35Gagarinite-(Y)NaCaYF6Hex. 6/m : P63/m
3.AB.35Polezhaevaite-(Ce)NaSrCeF6Hex. 6/m : P63/m
3.AB.35Gagarinite-(Ce)Na(REExCa1-x)(REEyCa1-y)F6Trig. 3 : P3
3.AB.37CalcioaravaipaitePbCa2AlF9Tric. 1 : P1
3.AB.85CotunnitePbCl2Orth. mmm(2/m2/m2/m)

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 ChloromagnesiteHide

References for ChloromagnesiteHide

Localities for ChloromagnesiteHide

Showing 6 localities.

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.
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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 (TL)
 
  • Campania
    • Metropolitan City of Naples
Palache et al. (1951)
Pelloux (1927) +2 other references
Poland
 
  • Silesian Voivodeship
    • Wodzisław County
      • Radlin
Kruszewski (2012)
Russia
 
  • Sakha
    • Mirninsky District
      • Daldyn
Sharygin et al. (2014)
USA
 
  • California
    • San Bernardino County
      • Ibex Hills
Bailey (1902) +1 other reference
  • Virginia
Dietrich (1990)
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