Bischofite

Bischofite is a hydrous magnesium chloride mineral with formula MgCl2·6H2O. It belongs to halides and is a sea salt concentrate. 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 bischofite 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
Bischofite from Antofagasta, Chile
General
CategoryHalide mineral
Formula
(repeating unit)		MgCl2·6H2O
IMA symbolBsf[1]
Strunz classification3.BB.15
Dana classification09.02.09.01
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/m
Identification
ColorColorless to white
Crystal habitFibrous to massive
Twinningpolysynthetic
CleavageNone
FractureConchoidal to uneven
Mohs scale hardness1.5–2
LusterVitreous – greasy
StreakWhite
DiaphaneityTranslucent to transparent
Specific gravity1.56
Optical propertiesBiaxial (+)
Refractive indexnα = 1.495
nβ = 1.507
nγ = 1.528
SolubilityDeliquescent
References[2][3][4]

History

Bischofite is named in honor of German geologist Gustav Bischof (1792–1870). Its discovery (1877) is attributed to Carl Christian Ochsenius.[5]

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.[6] Its composition can be explained by high content of magnesium chloride in the primordial ocean.[7]

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.[6]

Deposits

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.[3] 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.[4]

There are bischofite-rich deposits with concentrations of 93–96% of the mineral. One of those rare deposits is located in the Volgograd region of Russia. Another one was found in 1990s in the Poltava region in Ukraine. This is one of the deepest (2.5 km [1.6 mi]) and oldest bischofite deposits.[6]

Applications

Bischofite has many applications ranging from construction materials (tile, stone) to agriculture (preplant seeds, plant processing during vegetation period), oil extraction (for grouting and solidifying mortars), medical and chemical industry (production of magnesium metal).

Bischofite is used in form of compresses to treat joint diseases such as arthritis, rheumatic fever[8] osteoarthritis, rheumatoid arthritis, radiculitis, calcaneal spur and traumas, especially in rehabilitation centers in Ukraine, Russia, Belarus, and Lithuania. Bischofite is also applied in gel form.[6]

Bischofite is used in the production of the industrial Sorel cement[9] and synthetic carnallite. Bischofite solution is applied to deice roads,[9] similar to sodium chloride, but it is less corrosive. It is also used in agriculture, veterinary medicine and cattle breeding to increase the crop yield and treat animals.

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. Webmineral data
  3. Handbook of Mineralogy
  4. Bischofite on Mindat
  5. Ochsenius, C. (1877): Die Bildung der Steinsalzlager und ihrer Mutterlaugensalze unter specieller Berücksichtigung der Flöze von Douglashall in der Egeln´schen Mulde. Verlag Pfeffer (Halle), 172 p.
  6. A. A. Spasov (2003). Local bischofite therapy (PDF). Volgograd State University. ISBN 5-88462-065-9. Archived from the original (PDF) on 2010-10-09. Retrieved 2010-05-19.
  7. Hisahiro Ueda and Takazo Shibuya (2021). "Composition of the Primordial Ocean Just after Its Formation: Constraints from the Reactions between the Primitive Crust and a Strongly Acidic, CO2-Rich Fluid at Elevated Temperatures and Pressures". Minerals. Minerals 2021, 11(4), p. 389. 11 (4): 389. doi:10.3390/min11040389.
  8. Hans-Rudolf Wenk, Andreĭ Glebovich Bulakh (2004). Minerals: their constitution and origin. Cambridge University Press. p. 562. ISBN 0-521-52958-1.
  9. Mark A. Shand (2006). The chemistry and technology of magnesia. John Wiley and Sons. p. 216. ISBN 0-471-65603-8.

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