Mag­ne­site. Prop­er­ties and dis­tri­b­u­tion

Mag­ne­site is one of the most impor­tant min­er­als wide­ly used in var­i­ous indus­tries, includ­ing the pro­duc­tion of refrac­to­ry mate­ri­als, met­al­lur­gy, chem­i­cal and con­struc­tion indus­tries. Its unique prop­er­ties, such as high ther­mal sta­bil­i­ty, chem­i­cal inert­ness, and resis­tance to aggres­sive envi­ron­ments, make mag­ne­site indis­pens­able in process­es where high tem­per­a­tures and extreme con­di­tions are impor­tant.

Mag­ne­site 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 refrac­to­ry raw mate­r­i­al.

Mag­ne­site is a nat­ur­al mag­ne­sium car­bon­ate Mg(CO3), which in its pure form con­sists of 47.82% MgO and 52.18% CO₂, but usu­al­ly con­tains impu­ri­ties of cal­ci­um, man­ganese, and iron. Its main prop­er­ties include high melt­ing point, abra­sive­ness, and vis­cos­i­ty.

Physical and chemical properties

In met­al­lur­gy, two types of mag­ne­site refrac­to­ries are used: in the form of arti­fi­cial prod­ucts and in the form of met­al­lur­gi­cal pow­der. There are two types of mag­ne­sium car­bon­ate: amor­phous mag­ne­site with a small amount of impu­ri­ties and crys­talline mag­ne­site con­tain­ing impu­ri­ties of CaCO₃, FeCO₃, Al₂O₃, SiO₂ and oth­ers. The FeCO₃ con­tent in mag­ne­site usu­al­ly reach­es 8%, and dur­ing cal­ci­na­tion, iron acts as a min­er­al­iz­er, giv­ing the prod­ucts a brown­ish tint. Mag­ne­site raw mate­ri­als must under­go cal­ci­na­tion for com­plete decom­po­si­tion and removal of CO₂.

When heat­ed to 700‑1000°C, mag­ne­site los­es 92–98% of its car­bon diox­ide and turns into caus­tic mag­ne­sia (a pow­der con­sist­ing main­ly of MgO), which is wide­ly used in agri­cul­ture, in the pro­duc­tion of cer­tain types of cement, cel­lu­lose, paints, and in many oth­er sec­tors of the econ­o­my.

After anneal­ing mag­ne­site at a tem­per­a­ture of 1500–2000°C, almost all car­bon diox­ide is released and mag­ne­sium oxide crys­tal­lizes in the form of per­i­clase (MgO), which is the most valu­able refrac­to­ry mate­r­i­al used in met­al­lur­gi­cal, sul­fu­ric acid, and cement pro­duc­tion. At an even high­er tem­per­a­ture (2900°C), pure per­i­clase is obtained – an elec­tri­cal­ly insu­lat­ing heat-resis­tant mate­r­i­al.

High-qual­i­ty refrac­to­ries must con­tain the max­i­mum amount of per­i­clase and the min­i­mum amount of oth­er com­pounds. The most harm­ful impu­ri­ty is cal­ci­um oxide, an exces­sive amount of which neg­a­tive­ly affects the strength of refrac­to­ry prod­ucts. Sil­i­ca in the raw mate­r­i­al reduces the refrac­tori­ness and slag resis­tance of prod­ucts.

The pro­duc­tion of mag­ne­sia binders has become wide­spread. In many respects, mag­ne­sia binder raw mate­ri­als are an order of mag­ni­tude high­er than cement binders. Its unique­ness lies in the com­bi­na­tion of high bind­ing prop­er­ties and com­pat­i­bil­i­ty with vir­tu­al­ly any type of filler, includ­ing organ­ic nat­ur­al and arti­fi­cial ones. Caus­tic mag­ne­site, obtained after cal­ci­na­tion at rel­a­tive­ly low tem­per­a­tures of cer­tain nat­ur­al min­er­als con­tain­ing a sig­nif­i­cant amount of mag­ne­sium car­bon­ate or hydrox­ide (mag­ne­site, dolomite ), mixed with an aque­ous solu­tion of mag­ne­sium salts (mag­ne­sium sul­fate or chlo­ride — bischof­ite), forms a plas­tic mass with bind­ing prop­er­ties. Cement stone, formed on the basis of mag­ne­sia binder raw mate­ri­als, is a sol­id solu­tion of salts.

It is on the basis of mag­ne­sia binder raw mate­ri­als that var­i­ous stone-like mate­ri­als with pre­de­ter­mined prop­er­ties are obtained under the gen­er­al name “mag­no­lite.” Depend­ing on the fillers used, mag­notite has mechan­i­cal strength under com­pres­sion, on par with the most high-strength con­cretes, as well as a short set­ting time. Mag­ne­sia floor cov­er­ings are dust-free, have vir­tu­al­ly no shrink­age, are durable and high­ly resis­tant, have high hard­ness and low abra­sion, and are resis­tant to impact loads.

Distribution of magnesite in Ukraine

In Ukraine, the Prav­dyn­skoye tal­co­mag­ne­site deposit has been explored, and a num­ber of oth­er deposits and promis­ing ore occur­rences have been stud­ied.

The Prav­dynske deposit of tal­co­mag­ne­sites and car­bon­at­ed ser­pen­tinites is locat­ed in the Kryny­chan­skyi dis­trict of the Dnipropetro­vsk region 25 km from the city of Dnipro. The deposit is locat­ed in the south­east­ern part of the ultra-basic mas­sif of the same name in the Sursk syn­cli­nal struc­ture. The area has wide­ly devel­oped tec­ton­ic dis­tur­bances, which deter­mine its com­plex block struc­ture. Meta­mor­phic ortho-rocks of basic, medi­um, and acidic com­po­si­tion are interbed­ded with fer­rug­i­nous-car­bon­ate-siliceous and fer­rug­i­nous-siliceous shales.

Two types of ores have been iden­ti­fied at the deposit:

• 1) Talc-mag­ne­site rocks;
• 2) Car­bon­at­ed ser­pen­tinites.

The talc-mag­ne­site rocks of the deposit con­sist of talc (35–50%) and mag­ne­site (40–60%), with small amounts of ser­pen­tine, dolomite, chlo­rite, and mag­netite. Mag­ne­site (braen­ite) is observed in the form of aggre­gates and grains of iso­met­ric, angu­lar, and elon­gat­ed shapes. There is an uneven dis­tri­b­u­tion of the min­er­al in the rock. In areas of car­bon­ate-talc com­po­si­tion, the mag­ne­site con­tent decreas­es to 40–45%.

The pro­duc­tive thick­ness of the deposit with talc-mag­ne­sites and car­bon­at­ed ser­pen­tines lies among meta­mor­phic rocks. The length of this thick­ness is 800 m, and its thick­ness ranges from 80 to 350 m. Talc-mag­ne­sites do not expe­ri­ence sharp changes in thick­ness through­out the entire ter­ri­to­ry of the explored areas. The pro­ject­ed resources to a depth of 150 m are about 300 mil­lion tons. The max­i­mum thick­ness of the com­mer­cial lay­ers includ­ed in the reserve cal­cu­la­tion is 6 m.

Tech­no­log­i­cal stud­ies on the use and enrich­ment of talc-mag­ne­sites and car­bon­at­ed ser­pen­tinites have con­firmed the prof­itabil­i­ty of pro­duc­ing and using the fol­low­ing main com­mer­cial prod­ucts, includ­ing high-grade prod­ucts:
1 – mag­ne­site-braynite (40% yield) and grades A and B (48% yield) talc con­cen­trates for mul­ti­ple pur­pos­es, which are pro­duced by flota­tion enrich­ment;
2 – direct­ly obtained forsterite refrac­to­ries from talc-mag­ne­sites;
3 – fine­ly ground talc-mag­ne­site and car­bon­ate-ser­pen­tine flour, which can be sold as: a filler in var­i­ous indus­tries, insec­ti­cides for plant pro­tec­tion, a com­po­nent for heat-resis­tant con­crete, slag cast­ings, etc.; 4 – ore blocks from which sol­id-sawn refrac­to­ry bricks for rotary kilns can be pro­duced.

The Veselyanske deposit of talc-mag­ne­site is locat­ed on the left slope of the Kon­ka Riv­er near the vil­lage of Veselyan­ka in the Zapor­izhzhia region. The deposit con­sists of a com­bi­na­tion of ser­pen­tinites, talc-car­bon­ate, talc-chlo­rite, and chlo­rite-amphi­bole rocks of the Archean. Talc-mag­ne­site rocks pre­dom­i­nate in the deposit, which are sim­i­lar in qual­i­ty to those of the Pravdin­sky deposit. The total reserves of talc-mag­ne­site are 132 mil­lion tons, and the esti­mat­ed resources to a depth of 200 m are 250 mil­lion tons. The deposit is promis­ing and requires detailed explo­ration.

In addi­tion to lump cal­cined talc-mag­ne­site and ser­pen­ti­nite for the pro­duc­tion of forsterite refrac­to­ries, the talc-mag­ne­site deposits of Pravdin­sky and Veselyan­sky can be used to pro­duce float­ed talc and talc-mag­ne­site flour suit­able for the pro­duc­tion of plas­tics, paper, and roof­ing mate­ri­als; mag­ne­site con­cen­trate with a high con­tent of impu­ri­ties, which is used for the pro­duc­tion of mag­ne­sia refrac­to­ries, as well as iron ore con­cen­trate con­tain­ing alloy­ing ele­ments.

The role of mag­ne­site in indus­try can­not be over­es­ti­mat­ed, as its appli­ca­tion cov­ers key pro­duc­tion process­es involv­ing high tem­per­a­tures and aggres­sive con­di­tions. For Ukraine, ensur­ing a sta­ble sup­ply of high-qual­i­ty refrac­to­ry raw mate­ri­als is of great impor­tance. Expand­ing the coun­try’s mag­ne­site base and intro­duc­ing mod­ern approach­es to its ratio­nal use open up new prospects for indus­tri­al devel­op­ment.