Bischofite
| Bischofite | |
|---|---|
Bischofite from Antofagasta, Chile
|
|
| General | |
| Category | Halide mineral |
|
Formula (repeating unit) |
MgCl2·6H2O |
| Strunz classification | 3.BB.15 |
| Dana classification | 09.02.09.01 |
| Crystal system | Monoclinic |
| Crystal class | Prismatic (2/m) (same H-M symbol) |
| Space group | C2/m |
| Identification | |
| Color | Colorless to white |
| Crystal habit | Fibrous to massive |
| Twinning | polysynthetic |
| Cleavage | None |
| Fracture | Conchoidal to uneven |
| Mohs scale hardness | 1.5–2 |
| Luster | Vitreous – greasy |
| Streak | White |
| Diaphaneity | Translucent to transparent |
| Specific gravity | 1.56 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.495 nβ = 1.507 nγ = 1.528 |
| Solubility | Deliquescent |
| References | |
Bischofite (bischofit) is a hydrous magnesium chloride mineral with formula MgCl2·6H2O. It belongs to halides and is a sea salt concentrate dated from the Permian Period (nearly 200 million years ago). Bischofite is ecologically pure natural magnesium poly-mineral with a unique composition. It contains many macro- and micro-elements vital for human health, in much higher concentrations than can be found in sea or ocean salt. The main bischofit compound is magnesium chloride (up to 350 g/L), moreover, it contains about 70 other elements as impurities, including potassium, sodium, bromine, boron, calcium, silicon, molybdenum, silver, zinc, iron and copper.
Bischofite is named in honor of German geologist Gustav Bischof (1792–1870). Its discovery (1877) is attributed to Carl-Christian Ochsenius.
At its type locality bischofite it an evaporite formed in an ancient seabed, which was deposited more than 200 million years ago, during the Permian Period.
In 1930–1950, vast bischofite deposits were discovered near the Volga River in Russia. The mineral is mined by dissolving an underground dry mineral stratum with artesian water. The resulting brine is pumped out.
Bischofite deposits differ by their composition: some of them are salt basins where bischofite is mixed with other minerals such as carnallite, halite, kieserite and anhydrite. These are the so-called bischofite containing rocks which have pink-brown-yellow and orange-red colors. They contain 36–58% of bischofite. Carnallite deposits are known in Staßfurt, Germany – where bischofite was first discovered, and carnallite is one of the most important minerals in potassium salt deposits (Solykam deposit, Ural, Russia). Sub-surface bischofite layers were also discovered in Kazakhstan, Turkmenistan, China and the US.
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Wikipedia