Tachyhydrite
A valid IMA mineral species - grandfathered
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About Tachyhydrite
Formula:
CaMg2Cl6 · 12H2O
Colour:
Colourless, light yellow
Lustre:
Vitreous
Hardness:
2
Specific Gravity:
1.667
Crystal System:
Trigonal
Name:
From Greek ταχίς quick, and ϋδωρ, water, alluding to its ready deliquescence.
Type Locality:
A very hygroscopic hydrated chloride mineral.
Unique Identifiers
Mindat ID:
3865
Long-form identifier:
mindat:1:1:3865:8
GUID
(UUID V4):
(UUID V4):
3519c9fe-1718-40e4-8c7b-7f26018c539d
IMA Classification of Tachyhydrite
Approved, 'Grandfathered' (first described prior to 1959)
First published:
1856
Classification of Tachyhydrite
3.BB.35
3 : HALIDES
B : Simple halides, with H2O
B : M:X = 1:2
3 : HALIDES
B : Simple halides, with H2O
B : M:X = 1:2
11.5.5.1
11 : HALIDE COMPLEXES
5 : AmBX6
11 : HALIDE COMPLEXES
5 : AmBX6
8.4.6
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
4 : Halides of the alkaline earths and Mg
8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
4 : Halides of the alkaline earths and Mg
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 |
|---|---|---|
| Thy | 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 Tachyhydrite
Vitreous
Transparency:
Transparent
Colour:
Colourless, light yellow
Streak:
White
Hardness:
2 on Mohs scale
Cleavage:
Perfect
On {1011}.
On {1011}.
Density:
1.667 g/cm3 (Measured) 1.673 g/cm3 (Calculated)
Optical Data of Tachyhydrite
Type:
Uniaxial (-)
RI values:
nω = 1.520 nε = 1.512
Max Birefringence:
δ = 0.008
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:
Low
Pleochroism:
Non-pleochroic
Comments:
Not dichroic.
Chemistry of Tachyhydrite
Mindat Formula:
CaMg2Cl6 · 12H2O
Crystallography of Tachyhydrite
Crystal System:
Trigonal
Class (H-M):
3 - Rhombohedral
Space Group:
R3
Cell Parameters:
a = 10.136(1) Å, c = 17.318(2) Å
Ratio:
a:c = 1 : 1.709
Unit Cell V:
1,540.85 ų (Calculated from Unit Cell)
Z:
3
Morphology:
Massive; in rounded masses. Crystals rhombohedral with {0001} (artificial crystals).
Twinning:
Exhibits twin lamellae at times; probably secondary and due to pressure.
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
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
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2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
Stop | Start
Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
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) |
|---|---|---|---|---|---|---|---|
| 0009719 | Tachyhydrite | Leclaire A, Borel M, Monier J (1980) Structure de la tachydrite _cod_database_code 1001774 Acta Crystallographica B36 2734-2735 |  | 1980 | 0 | 293 | |
| 0009720 | Tachyhydrite | Clark J R, Evans H T, Erd R C (1980) Tachyhydrite, dimagnesium calcium chloride 12-hydrate Acta Crystallographica B36 2736-2739 | | 1980 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.884 Å | (100) |
| 5.77 Å | (35) |
| 2.609 Å | (25) |
| 1.443 Å | (25) |
| 1.983 Å | (20) |
| 5.07 Å | (12) |
| 3.097 Å | (10) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) |
Geological Setting:
Oceanic type potash-rich saline deposits.
Type Occurrence of Tachyhydrite
Place of Conservation of Type Material:
No defined type material.
Geological Setting of Type Material:
Oceanic-type, potash-rich saline deposit.
Associated Minerals at Type Locality:
Reference:
Rammelsberg C (1856) Ueber den tachhydrit, ein neues mineral aus dem Steinsalzlager von Stassfurth. Annalen der Physik und Chemie 98, 261-263
Other Language Names for Tachyhydrite
Common Associates
Associated Minerals Based on Photo Data:
| 2 photos of Tachyhydrite associated with Carnallite | KMgCl3 · 6H2O |
Related Minerals - Strunz-mindat Grouping
| 3.BB.05 | Eriochalcite | CuCl2 · 2H2O |
| 3.BB.10 | Rokühnite | FeCl2 · 2H2O |
| 3.BB.15 | Bischofite | MgCl2 · 6H2O |
| 3.BB.20 | Nickelbischofite | NiCl2 · 6H2O |
| 3.BB.25 | Sinjarite | CaCl2 · 2H2O |
| 3.BB.30 | Antarcticite | CaCl2 · 6H2O |
| 3.BB.35 | Aravaipaite | Pb3AlF9 · H2O |
| 3.BB.40 | Ghiaraite | CaCl2 · 4H2O |
Other Information
Notes:
Readily soluble in water.
Special Storage/
Display Requirements:
Display Requirements:
Very deliquescent.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:
Source of potassium.
Internet Links for Tachyhydrite
mindat.org URL:
https://www.mindat.org/min-3865.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Tachyhydrite
Reference List:
Localities for Tachyhydrite
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.
Austria | |
| Strasser (1989) |
Brazil | |
| www.cetem.gov.br (n.d.) |
Chile | |
| Cabestrero et al. (2022) |
Eurasian Plate | |
| Wang et al. (2017) |
Germany | |
| Weiß (1990) |
| Füchtbauer et al. (1956) |
| Weiß (1990) |
| Niemann (1960) |
| Bode "Mineralien und Fundstellen BRD" ... |
| Dana 6: Appendix 3: 40 +1 other reference |
| Palache et al. (1951) |
| |
| Palache et al. (1951) +1 other reference | |
Poland | |
| Wachowiak et al. (2016) |
Republic of the Congo | |
| Zhao et al. (2016) |
| Henry Rauche (2009) | |
| Milesi et al. (2006) | |
Russia | |
| Vergasova et al. (1977) +1 other reference |
Thailand | |
| Tabakh et al. (1998) |
| Suwanich (2010) |
UK | |
| Mineralogical Magazine 1959 32 : ... |
USA | |
| Northrop et al. (1996) |
| Hawley +5 other references |
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Brefeld potash mine, Tarthun, Bördeaue, Salzlandkreis, Saxony-Anhalt, Germany