Calomel
A valid IMA mineral species - grandfathered
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About Calomel
Formula:
[Hg2]2+Cl2
Colour:
Colourless, white, grayish, yellowish white, yellowish grey to ash-grey, brown; darkens upon exposure to light
Lustre:
Adamantine
Hardness:
1½ - 2
Specific Gravity:
7.15
Crystal System:
Tetragonal
Member of:
Name:
From Greek kalos = beautiful and melos = black, because it turns black when it comes into contact with ammonia. This reaction, which was already known to the alchemists centuries ago, is used as a test for mercury(I).
Unique Identifiers
Mindat ID:
869
Long-form identifier:
mindat:1:1:869:1
GUID
(UUID V4):
(UUID V4):
182b710f-1611-4596-8ff4-07a826492384
IMA Classification of Calomel
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
HgCl
Classification of Calomel
3.AA.30
3 : HALIDES
A : Simple halides, without H2O
A : M:X = 1:1, 2:3, 3:5, etc.
3 : HALIDES
A : Simple halides, without H2O
A : M:X = 1:1, 2:3, 3:5, etc.
9.1.8.1
9 : NORMAL HALIDES
1 : AX
9 : NORMAL HALIDES
1 : AX
8.5.2
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
5 : Halides of Zn and Hg
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
5 : Halides of Zn and Hg
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 |
---|---|---|
Clo | 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 Calomel
Adamantine
Transparency:
Transparent
Colour:
Colourless, white, grayish, yellowish white, yellowish grey to ash-grey, brown; darkens upon exposure to light
Streak:
Light yellowish white
Hardness:
1½ - 2 on Mohs scale
Tenacity:
Sectile
Cleavage:
Distinct/Good
{110} good but slightly uneven; {011} imperfect.
{110} good but slightly uneven; {011} imperfect.
Fracture:
Conchoidal
Density:
7.15 g/cm3 (Measured) 7.23 g/cm3 (Calculated)
Optical Data of Calomel
Type:
Uniaxial (+)
RI values:
nω = 1.973 nε = 2.656
Max Birefringence:
δ = 0.683
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
Very High
Pleochroism:
Weak
Comments:
Absorption E greater than O.
Comments:
Mechanically deformed crystals may exhibit optical anomalies.
Chemistry of Calomel
Mindat Formula:
[Hg2]2+Cl2
Elements listed:
Crystallography of Calomel
Crystal System:
Tetragonal
Class (H-M):
4/mmm (4/m 2/m 2/m) - Ditetragonal Dipyramidal
Space Group:
I4/mmm
Cell Parameters:
a = 4.4795(5) Å, c = 10.9054(9) Å
Ratio:
a:c = 1 : 2.435
Unit Cell V:
218.83 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Crystals often tabular {001}; prismatic [001]; pyramidal; equant, especially in complex twins. Complex development often exhibited. Drusy crusts of minute crystals. Massive, earthy.
Twinning:
On {112}. As contact or interpenetrant twins often repeated and with irregular and concealed boundaries.
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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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) |
---|---|---|---|---|---|---|---|
0010993 | Calomel | Calos N J, Kennard C H L, Davis R L (1989) The structure of calomel, Hg2Cl2, derived from neutron powder data Zeitschrift fur Kristallographie 187 305-307 | 1989 | 0 | 293 | ||
0011656 | Calomel | Wyckoff R W G (1963) Second edition. Interscience Publishers, New York, New York Crystal Structures 1 85-237 | 1963 | 0 | 293 | ||
0017968 | Calomel | Havighurst R (1925) Crystal structure of the mercurous halides _cod_database_code 1011069 American Journal of Science 10 15-28 | 1925 | 0 | 293 | ||
0017974 | Calomel | Havighurst R (1926) Parameters in crystal structure. The mercurous halides _cod_database_code 1011076 Journal of the American Chemical Society 48 2113-2130 | 1926 | 0 | 293 | ||
0017669 | Calomel | Hylleraas E (1926) Die Anordnung der Atome in den tetragonalen Kristallen der einwertigen Quecksilberhalogenide Hg2 Cl2, Hg2 Br2, Hg2 J2. Berechnung der optischen Doppelbrechung von Hg2 Cl2. _cod_database_code 1010948 Zeitschrift fur Physik 36 859-896 | 1926 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
d-spacing | Intensity |
---|---|
3.170 Å | (100) |
4.15 Å | (75) |
2.067 Å | (40) |
2.727 Å | (30) |
1.962 Å | (30) |
1.970 Å | (16) |
2.824 Å | (12) |
Comments:
Synthetic.
Geological Environment
Paragenetic Mode(s):
Paragenetic Mode | Earliest Age (Ga) |
---|---|
Stage 7: Great Oxidation Event | <2.4 |
47g : [Halogen-bearing surface weathering minerals] |
Geological Setting:
Uncommon in the secondary weathering zones of mercury deposits.
Type Occurrence of Calomel
Synonyms of Calomel
Other Language Names for Calomel
Relationship of Calomel to other Species
Member of:
Other Members of this group:
Kuzminite | [Hg2]2+(Br,Cl)2 | Tet. 4/mmm (4/m 2/m 2/m) : I4/mmm |
Moschelite | [Hg2]2+I2 | Tet. 4/mmm (4/m 2/m 2/m) : I4/mmm |
Forms a series with:
Common Associates
Associated Minerals Based on Photo Data:
25 photos of Calomel associated with Cinnabar | HgS |
16 photos of Calomel associated with Mercury | Hg |
14 photos of Calomel associated with Eglestonite | [Hg2]2+3OCl3(OH) |
8 photos of Calomel associated with Quartz | SiO2 |
5 photos of Calomel associated with Terlinguaite | [Hg3]4+Hg2+Cl2O2 |
3 photos of Calomel associated with Calcite | CaCO3 |
3 photos of Calomel associated with Chalcedony | SiO2 |
1 photo of Calomel associated with Gianellaite | [(Hg2N)2](SO4)(H2O)x |
1 photo of Calomel associated with Cristobalite | SiO2 |
1 photo of Calomel associated with Corderoite | Hg2+3S2Cl2 |
Related Minerals - Strunz-mindat Grouping
3.AA. | Brontesite | (NH4)3PbCl5 |
3.AA.05 | Marshite | CuI |
3.AA.05 | Miersite | (Ag,Cu)I |
3.AA.05 | Nantokite | CuCl |
3.AA.05 | UM1999-11:I:CuS | Cu(I,S) |
3.AA.10 | Iodargyrite | AgI |
3.AA.10 | Tocornalite | (Ag,Hg)I |
3.AA.15 | Bromargyrite | AgBr |
3.AA.15 | Chlorargyrite | AgCl |
3.AA.20 | Carobbiite | KF |
3.AA.20 | Griceite | LiF |
3.AA.20 | Halite | NaCl |
3.AA.20 | Sylvite | KCl |
3.AA.20 | Villiaumite | NaF |
3.AA.25 | Salammoniac | NH4Cl |
3.AA.25 | UM1998-03-Cl:Tl | TlCl |
3.AA.25 | Lafossaite | Tl(Cl,Br) |
3.AA.25 | Nataliyamalikite | TlI |
3.AA.30 | Kuzminite | [Hg2]2+(Br,Cl)2 |
3.AA.30 | Moschelite | [Hg2]2+I2 |
3.AA.35 | Neighborite | NaMgF3 |
3.AA.35 | Parascandolaite | KMgF3 |
3.AA.40 | Chlorocalcite | KCaCl3 |
3.AA.40 | Javorieite | KFeCl3 |
3.AA.45 | Kolarite | PbTeCl2 |
3.AA.50 | Radhakrishnaite | PbTe3(Cl,S)2 |
3.AA.55 | Challacolloite | KPb2Cl5 |
3.AA.60 | Hephaistosite | TlPb2Cl5 |
3.AA.90 | Pseudocotunnite | K2PbCl4 |
Fluorescence of Calomel
Brick-red (UV)
Other Information
Thermal Behaviour:
Thermally positive.
Health Risks:
Contains mercury - always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest.
Industrial Uses:
Ore of mercury.
Calomel in petrology
An essential component of rock names highlighted in red, an accessory component in rock names highlighted in green.
Internet Links for Calomel
mindat.org URL:
https://www.mindat.org/min-869.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Calomel
Reference List:
Localities for Calomel
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).
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.
All localities listed without proper references should be considered as questionable.
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Quick NavTopAbout CalomelUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesRelationshipsCommon AssociatesStrunz-MindatFluorescence Other InformationCalomel in petrologyInternet Links References Localities Locality List
Mariposa Mine, Brewster County, Texas, USA