Tachyhydrite
General
CategoryHalide minerals
Formula
(repeating unit)		CaMg2Cl6·12H2O
IMA symbolThy[1]
Strunz classification3.BB.35
Crystal systemTrigonal
Crystal classRhombohedral 3
H-M symbol: 3
Space groupR3
Identification
ColorColorless, light yellow
Lustervitreous
Diaphaneitytransparent
References[2][3]

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 crystal 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.[4]

According to a patent filed years ago by a Halliburton researcher, high strength hydrochloric acid treatment of magnesium containing carbonates creates tachyhydrite, which will seal the rock pores and inhibit oil flow unless washed with a light acid or water before and after the treatment.[5]

References

  1. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ↑ Mindat
  3. ↑ Mineralienatlas
  4. ↑ Webmineral data
  5. ↑ Patent


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