Tachyhydrite
Encyclopedia
Tachyhydrite is an unstable mineral, a hydrous chloride
of calcium
and magnesium
with formula: Ca
Mg
2Cl
6·12H2O
. 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.
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.
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
of calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
and magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
with formula: Ca
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
Mg
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
2Cl
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
6·12H2O
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
. It is a rare component of marine evaporite
Evaporite
Evaporite is a name for a water-soluble mineral sediment that result from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporate deposits, marine which can also be described as ocean deposits, and non-marine which are found in standing bodies of...
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
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
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
Saxony
The Free State of Saxony is a landlocked state of Germany, contingent with Brandenburg, Saxony Anhalt, Thuringia, Bavaria, the Czech Republic and Poland. It is the tenth-largest German state in area, with of Germany's sixteen states....
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. Its name is from the Greek for quick water, in reference to its ready deliquescence.
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.