Tachyhydrite

Tachyhydrite is an unstable mineral, a hydrous chloride of calcium and magnesium with formula: CaMg2Cl6·12H2O. It is a rare component of marine evaporite salt deposits. Upon exposure to moist air it rapidly deliquesces and dissolves.It forms a colorless to yellow trigonal crystals with a vitreous luster. It is soft with a Mohs hardness of 2 and has a low specific gravity of 1.66. It has good cleavage in three directions and typically occurs in crystalline masses.It was first described in 1856 for an occurrence in Stassfurt, Saxony, Germany. Its name is from the Greek for quick water, in reference to its ready deliquescence.
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General Information:
 Chemical Formula:
CaMg2Cl6·12(H2O)
 Composition:
(Molecular Weight = 517.59 gm)
Calcium 7.74 % Ca
Magnesium 9.39 % Mg
Hydrogen 4.67 % H 
Chlorine 41.10 % Cl
Oxygen 37.09 % O 
 Empirical Formula:
CaMg2Cl6·12(H2O)
 Environment:
Rare constituent of marine salt deposits.
 Locality:
Stassfurt, Province of Saxony, Germany.
 Name Origin:
From the Greek for "quick water", in allusion to its ready deliquescence.
Physical Properties:
 Cleavage:
[1011] Good, [1011] Good, [1011] Good
 Color:
colorless or yellow.
 Density:
1.66
 Diaphaniety:
Transparent to translucent
 Habits:
Massive - Uniformly indistinguishable crystals forming large masses., Deliquescent - Crystals absorb water from the air and melt or otherwise deteriorate., Tastes Bitter - Bitter tast e from water soluble Mg or Ca compounds.
 Hardness:
2 - Gypsum
 Luster:
Vitreous - Greasy
 Streak:
white
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