Bischof­ite is a hydrous mag­ne­sium chlo­ride, MgCl₂·6H₂O. In its pure form, its crys­tals are trans­par­ent, but depend­ing on the impu­ri­ties present, they may range in col­or from white to brown. Although crys­talline bischof­ite is rel­a­tive­ly rare, it is most com­mon­ly found in nature as high­ly min­er­al­ized brines (bischof­ite brines) pre­served in closed salt-bear­ing struc­tures at depth.

Bischof­ite is the final prod­uct of halo­ge­n­e­sis, form­ing at the last stage of the devel­op­ment of sul­fate-type salt deposits rich in mag­ne­sium. It may some­times con­tain bromine impu­ri­ties of up to 1%. It crys­tal­lizes in the mon­o­clin­ic sys­tem. It has a glassy or dull lus­ter and is brit­tle, with no cleav­age. It is hygro­scop­ic and del­i­quesces when exposed to air, espe­cial­ly in cold con­di­tions. It is high­ly sol­u­ble in water and alco­hol. Genet­i­cal­ly, it is main­ly an evap­or­ite sed­i­men­ta­ry chem­i­cal (chemogenic) min­er­al. It is extract­ed main­ly by in-situ dis­so­lu­tion min­ing. Bischof­ite forms near­ly monomin­er­al­ic bischof­ite rocks, as well as bischof­ite-halite, bischof­ite-car­nal­lite, and bischof­ite-kieserite rocks.

Bischof­ite is includ­ed in the list of min­er­als of nation­al impor­tance, approved by Res­o­lu­tion of the Cab­i­net of Min­is­ters of Ukraine No. 827 of Decem­ber 12, 1994, as a chem­i­cal raw mate­r­i­al and a com­po­nent for drilling flu­id prepa­ra­tion.

Bischof­ite was first dis­cov­ered in 1877 in the Stass­furt salt deposits in Ger­many by the Ger­man geol­o­gist and chemist Karl Ochse­nius. The min­er­al was named after the Ger­man geol­o­gist Gus­tav Bischof to com­mem­o­rate his con­tri­bu­tions to 19th-cen­tu­ry chem­istry and geol­o­gy in Ger­many.

In the first decades after its dis­cov­ery, bischof­ite was con­sid­ered a rare min­er­al. How­ev­er, in the 1930s–1950s, large deposits were iden­ti­fied in the Vol­ga region, and in the 1990s the old­est and deep­est bischof­ite deposit was dis­cov­ered in the Polta­va region of Ukraine, at a depth of about 2.5 km.

Nat­ur­al accu­mu­la­tions of bischof­ite are known only in a few loca­tions world­wide: Turk­menistan (Kara-Bogaz-Gol Bay), Israel (Dead Sea), Rus­sia (Vol­gograd region and Astrakhan area — brines of Lake Mal­oe Liman­skoye), Ukraine (Polta­va and Cherni­hiv regions), and Bul­gar­ia (brines of Lake Pomorie).

The main glob­al resources of bischof­ite are asso­ci­at­ed with the Low­er Per­mi­an (Artinskian–Kungurian) evap­or­ite for­ma­tion of the Pre-Caspi­an Syneclise (e.g., the Gorodishche deposit), although pro­duc­tive lay­ers (up to 1–2 m thick) are also known in potash salt deposits in Ger­many, the Nether­lands, Gabon, Brazil, Con­go, and Moroc­co.

Bischof­ite deposits dif­fer in com­po­si­tion: some occur with­in salt basins where it is mixed with oth­er min­er­als such as car­nal­lite, halite, kieserite, and anhy­drite. These so-called bischof­ite-bear­ing rocks are pink­ish-brown, yel­low, and orange-red in col­or and con­tain 36–58% bischof­ite. Sub­sur­face lay­ers have also been iden­ti­fied in Kaza­khstan, Turk­menistan, Chi­na, and the Unit­ed States.

There are also high-grade deposits con­tain­ing 93–96% bischof­ite. One such rare deposit was dis­cov­ered in the 1990s in the Polta­va region of Ukraine. It is one of the deep­est (2.5 km) and old­est bischof­ite deposits.

Ukraine’s resources exceed 50 km³ and are asso­ci­at­ed with the Kram­a­torsk For­ma­tion of the Dnieper–Donets Basin, where a bischof­ite lay­er (4–30 m thick) occurs at depths of 1,800–2,600 m. Two main areas of dis­tri­b­u­tion are dis­tin­guished: the north­west­ern part of the basin (Chernihiv–Ichnia area) and the south­east­ern part (Polta­va area and east­ward), both relat­ed to inter­nal zones of large salt basins (Koshelivka–Vertiivka, Srib­ne, Orchyt­sia depres­sions).

The State Bal­ance of Reserves includes the Zatu­rynske and Novopodil­sk deposits. Pilot indus­tri­al pro­duc­tion is car­ried out at the Zatu­rynske, Novopodil­sk, East-Polta­va, and Vatazhky deposits.

Bal­ance reserves of raw ore amount to 94 mil­lion tons (cat­e­go­ry C2). In the com­ing years, pro­duc­tion of bischof­ite brine is planned to reach 400,000 tons per year. Explo­ration work is ongo­ing at the Vatazhky, Parafiivka–Karpylivka, Monastyryshche–Olshanka, and Mashiv­ka areas to assess prospec­tive resources and indus­tri­al reserves.

The Zatu­rynske deposit is locat­ed with­in the Orchyt­sia depres­sion, where a thick (14.5–24 m) bischof­ite hori­zon occurs over an area of about 200 hectares at depths of 2,856–2,678 m. Min­er­al com­po­si­tion (%): bischof­ite — 88.47; halite — 8.53; kieserite — 1.87; gyp­sum — 0.82; oth­er salts — 0.31. Total brine salin­i­ty is 371.89 g/L. Bal­ance reserves of crude bischophyte ore by cat­e­go­ry C₂ are equal to 19 mil­lion tons, brine bischophyte by cat­e­go­ry C₁ 720 m³/month, C₂ 1450 m³/month. Research and pro­duc­tion exploita­tion began in 1993; 8,677 m³ of brine were mined in 3 years.

The Novopodil­sk deposit is locat­ed with­in the Ivan­horod depres­sion, where a 10–30 m thick salt-bear­ing hori­zon of the Low­er Per­mi­an Kram­a­torsk For­ma­tion lies at a depth of about 2,000 m. Com­po­si­tion: bischof­ite (37–96%), kieserite (1–49%), halite (2–47%). Brine den­si­ty ranges from 1.27 to 1.80 g/cm³. Pre-explored reserves and resources of crude ore of the deposit amount to 7.5 mil­lion tons under cat­e­go­ry C₂; P₁ — 302.4 mil­lion tons.

Bischof­ite is con­sid­ered an envi­ron­men­tal­ly safe sub­stance; there­fore, its use does not cause neg­a­tive impacts on the envi­ron­ment. Due to the large num­ber of deposits in Ukraine and the sim­ple extrac­tion tech­nol­o­gy (drilling and pump­ing brine to the sur­face), its pro­duc­tion is eco­nom­i­cal­ly effi­cient.

It is a valu­able and inex­pen­sive raw mate­r­i­al for obtain­ing mag­ne­sium and its com­pounds, as well as for the pro­duc­tion of mag­ne­sian cement. It is also used for impreg­nat­ing wood to improve its strength. About 99% of bischof­ite is extract­ed for tech­ni­cal pur­pos­es, while less than 1% from the Polta­va deposit is specif­i­cal­ly used in med­i­cine and sana­to­ri­um-resort treat­ment.

Bischof­ite is wide­ly applied in the treat­ment of dis­eases of the mus­cu­loskele­tal sys­tem, ner­vous sys­tem, and car­dio­vas­cu­lar sys­tem. It is also used as an adap­to­genic, anti-stress, and seda­tive agent (for exam­ple, in ther­a­peu­tic baths).

In indus­try, bischof­ite is used as an addi­tive in con­crete, as a drilling flu­id com­po­nent, as a cor­ro­sion inhibitor, and in the pro­duc­tion of mag­ne­sium-con­tain­ing com­pounds. In agri­cul­ture, it serves as a mag­ne­sium fer­til­iz­er that improves soil fer­til­i­ty. It is also used in the ener­gy sec­tor for water purifi­ca­tion and in every­day prod­ucts such as bath addi­tives and cos­met­ic creams.

Bischof­ite is a unique min­er­al with a wide range of applications—from indus­try to med­i­cine. Thanks to sig­nif­i­cant reserves, espe­cial­ly in Ukraine, and sim­ple extrac­tion meth­ods, it is an impor­tant raw mate­r­i­al for the pro­duc­tion of mag­ne­sium, cement, fer­til­iz­ers, cor­ro­sion inhibitors, and med­i­c­i­nal prod­ucts. The most promis­ing deposits are the Zatu­rynske and Novopodil­sk deposits in the Polta­va region, which are char­ac­ter­ized by high bischof­ite con­cen­tra­tion and large reserves.