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Tachyhydrite

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Formula:
CaMg
 
2
Cl
 
6
· 12H
 
2
O
System:TrigonalColour:Colourless, light yellow
Lustre:VitreousHardness:2
Name:From Greek ταχίς quick, and ϋδωρ, water, alluding to its ready deliquescence.


A very hygroscopic hydrated chloride mineral.

Classification of Tachyhydrite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:3/C.08-30
Nickel-Strunz 10th (pending) edition ID:3.BB.35

3 : HALIDES
B : Simple halides, with H2O
B : M:X = 1:2
Dana 8th edition ID:11.5.5.1

11 : HALIDE COMPLEXES
5 : AmBX6
Hey's CIM Ref.:8.4.6

8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
4 : Halides of the alkaline earths and Mg
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Type Occurrence of Tachyhydrite

Type Locality:Stassfurt, Stassfurt Potash deposit, Saxony-Anhalt, Germany
Year of Discovery:1856
Geological Setting of type material:Oceanic-type, potash-rich saline deposit.
Associated Minerals at type locality:
KainiteCarnallite

Occurrences of Tachyhydrite

Geological Setting:Oceanic type potash-rich saline deposits.

Physical Properties of Tachyhydrite

Lustre:Vitreous
Diaphaneity (Transparency):Transparent
Colour:Colourless, light yellow
Hardness (Mohs):2
Cleavage:Perfect
On {10_11}.
Density (measured):1.667 g/cm3

Crystallography of Tachyhydrite

Crystal System:Trigonal
Morphology:Massive; in rounded masses. Crystals rhombohedral with {0001} (artificial crystals).
Twinning:Exhibits twin lamellae at times; probably secondary and due to pressure.

Optical Data of Tachyhydrite

Type:Uniaxial (-)
RI values: nω = 1.520 nε = 1.512
Maximum Birefringence:δ = 0.008

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Low
Pleochroism:Non-pleochroic
Comments:Not dichroic.

Chemical Properties of Tachyhydrite

Formula:
CaMg
 
2
Cl
 
6
· 12H
 
2
O
Simplified for copy/paste:CaMg2Cl6·12H2O
Essential elements:Ca, Cl, H, Mg, O
All elements listed in formula:Ca, Cl, H, Mg, O
Analytical Data:Very deliquescent.

Relationship of Tachyhydrite to other Species

Common Associates:
SylviteKieseriteKainiteHaliteCarnallite
BischofiteAnhydrite
Related Minerals - Nickel-Strunz Grouping):

- +
3.BB.05Eriochalcite
CuCl
 
2
· 2H
 
2
O
3.BB.10Rokühnite
FeCl
 
2
· 2H
 
2
O
3.BB.15Bischofite
MgCl
 
2
· 6H
 
2
O
3.BB.20Nickelbischofite
NiCl
 
2
· 6H
 
2
O
3.BB.25Sinjarite
CaCl
 
2
· 2H
 
2
O
3.BB.30Antarcticite
CaCl
 
2
· 6H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
8.4.1Sellaite
MgF
 
2
8.4.2Neighborite
NaMgF
 
3
8.4.3Bischofite
MgCl
 
2
· 6H
 
2
O
8.4.4Korshunovskite
Mg
 
2
Cl(OH)
 
3
· 4H
 
2
O
8.4.5Carnallite
KMgCl
 
3
· 6H
 
2
O
8.4.7Fluorite
CaF
 
2
8.4.8Sinjarite
CaCl
 
2
· 2H
 
2
O
8.4.9Antarcticite
CaCl
 
2
· 6H
 
2
O
8.4.10Chlorocalcite
KCaCl
 
3
8.4.11Rorisite
CaFCl
8.4.12Jarlite
Na(Sr,Na)
 
7
MgAl
 
6
F
 
32
(OH,H
 
2
O)
 
2
8.4.13Calcjarlite
Na(Ca,Sr)
 
3
Al
 
3
(OH)
 
2
F
 
14
8.4.14Tikhonenkovite
Sr[AlF
 
4
(OH)(H
 
2
O)]
8.4.15Acuminite
Sr[AlF
 
4
(OH)(H
 
2
O)]
8.4.16Frankdicksonite
BaF
 
2
8.4.17Usovite
Ba
 
2
CaMgAl
 
2
F
 
14
8.4.18Bøgvadite
Na
 
2
SrBa
 
2
Al
 
4
F
 
20

Other Names for Tachyhydrite

Other Languages:
German:Tachyhydrit
Russian:Тахигидрит
Spanish:Tachyhydrita

Other Information

Other Information:Readily soluble in water.
Health Warning: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.

References for Tachyhydrite

Reference List:

- +
Rammelsberg (1856) Annalen der Physik, Halle, Leipzig: 98: 261.

Des Cloizeaux, A. (1867) Nouvelles recherches sur les propriétés optique des cristaux, naturels ou artificiels, et sur les variations que ces propriétés éprouvent sous l’influence de la chaleur. 222pp., Paris. (Institut imperial de France, Mémoires 18): 74.

Groth, P. (1874) Tabellarische Übersicht der Mineralien nach ihren krystallographish-chemischen Beziehungen. Braunschweig. 1st. edition: 74.

de Schulten (1890) Comptes rendus de l’Académie des sciences de Paris: 111: 928.

Boeke (1908) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 45: 354.

Kling (1915) Centralblatt für Mineralogie, Geologie und Paleontologie, Stuttgart: 14, 44.

Jung (1926) Centralblatt für Mineralogie, Geologie und Paleontologie, Stuttgart: 274.

Doelter, C. (1928) Handbuch der Mineral-chemie (in 4 volumes divided into parts): 4[2]: 1219.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 95-96.

Acta Crystallographica (1980): B36: 2736-2739.

Internet Links for Tachyhydrite

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  • Localities for Tachyhydrite

    The 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.
    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    Austria
     
    • Salzburg
      • Hallein
        • Dürrnberg
    A. Strasser: Die Minerale Salzburgs, 1989
    Germany
     
    • Lower Saxony
      • Celle
        • Hänigsen
    Bode "Mineralien und Fundstellen BRD" from 1989 ISBN 3-925094-24-5 Pg.9
        • Wathlingen
    Weiss: "Mineralfundstellen, Deutschland West", Weise (Munich), 1990
      • Göttingen
        • Reyershausen
    Niemann, H. (1960): Contributions to Mineralogy and Petrology 7, 137-165.
      • Nordhorn
        • Frenswegen
    Füchtbauer, H., and Goldschmidt, H. (1956): Contributions to Mineralogy and Petrology 5(3), 187-203.
      • Peine
    Dana 6: Appendix 3: 40; Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 91.
      • Vienenburg
    Weiss: "Mineralfundstellen, Deutschland West", Weise (Munich), 1990
    • Saxony-Anhalt
      • Halle
        • Teutschenthal
    Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 95.
      • Stassfurt Potash deposit
        • Egeln
          • Tarthun
    No reference listed
    Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II: 95; Wittern: "Mineralfundorte in Deutschland", 2001
    Republic of Congo (Brazzaville)
     
    • Kouilou Department
    Henry Rauche (2009) Updated Reserve and Resource Estimate for MagMinerals Kouilou Potash Project, Republic of Congo
    UK
     
    • England
      • Co. Durham
        • Billingham
    Mineralogical Magazine 1959 32 : 172-175.
    USA
     
    • New Mexico
      • Eddy and Lea Counties
    Northrop, Minerals of New Mexico, 3rd. rev. ed. (1996)
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