Tachyhydrite

• Tachhydrite

• CaMg2Cl6 · 12H2O
• Oxide formula: CaCl2 · 12H2O · 2MgCl2

Tachyhydrit (also tachhydrite ) is a rarely occurring mineral from the mineral class of " halides ". It crystallizes in the trigonal crystal system with the composition CaMg2Cl6 · 12H2O, is thus seen chemically a hydrous calcium magnesium chloride.

Tachyhydrit is transparent to translucent and usually develops rounded, colorless or wax to honey yellow masses. Drawn Synthetic forms the mineral also rhombohedral or tabular crystals.

With a Mohs hardness of 2 Tachyhydrit belongs to the soft minerals and is similar to the reference mineral plaster with a fingernail scratch.

Special Features

The mineral is readily soluble in water, ie one liter of water with a temperature of 18.75 ° C can hold 1603 grams Tachyhydrit.

Etymology and history

Tachyhydrit owes its name to its hygroscopic property to remove the ambient air, the moisture and then melt away quickly. The name was derived from the Ancient Greek words ταχύς [ tachýs ] for fast and ὕδωρ [ hydor ] for water, ie composed "fast water ".

Was first discovered the mineral in the rock salt deposit at Staßfurt in Saxony -Anhalt and described in 1856 by Karl Friedrich Rammelsberg.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Tachyhydrit belonged to the department of " Doppelhalogenide (usually with OH, H2O) " where he along with the carnallite " carnallite Tachyhydrit group " with the System No.. Formed III/C.08 and the other members koenenite and Redikortsevit.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Tachyhydrit other hand, in the department of the " Simple halides with H2O". This is also further subdivided by the molar ratio of metal (M) to each halogen (X), so that the mineral according to its composition in the subsection "M: X = 1: 2" to find where it is the only member of the unnamed group 3.BB.35 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the Tachyhydrit likewise in the class of " halides ", there, however, in the department of " complexes halides - Aluminium Fluoride " a. Here he is the only member of the unnamed group 11:05:05 within the sub-division of " complexes halides - aluminum fluorides with (A) mB (X ) 6" to find.

Education and Locations

Tachyhydrit separates out from strong magnesium-containing residual liquors of marine salt deposits. Accompanying minerals occur among others anhydrite, bishofite, carnallite, halite, kainite and sylvite and Kieserit.

A rare mineral formation Tachyhydrit previously could (as of 2012) are detected only at a few localities, with slightly more than 10 localities as have been established. Apart from its type locality Staßfurt the mineral came to light in Germany nor in Tarthun and potash Kruger Hall Teutschenthal in Saxony- Anhalt as well as in several potash mines near Celle, Reyershausen ( potash King Hall Hindenburg ), Frenswegen, Peine ( potash Desdemona ) and potash Vienenburg.

The previously only Austrian locality is the rock salt deposit at Dürr mountain in Salzburg.

Furthermore, it was found Tachyhydrit still in the pit box Mengo in the department Kouilou the Republic of Congo, in the Anhydritgrube Billingham and potash in Carlsbad Eddy County of the U.S. state of New Mexico.

Crystal structure

Tachyhydrit trigonal crystallized in the space group R3 ( Raumgruppen-Nr. 148) with the lattice parameters a = 10.14 Å and c = 17.32 Å and 3 formula units per unit cell.

Use

A patent describes how to form magnesium- carbonates by treatment with strong hydrochloric acid Tachyhydrit. This closes the pores and prevent the passage of oil, if it is not washed off with water or weak acid.