Gyp­sum. Char­ac­ter­is­tics, types, dis­tri­b­u­tion

Gyp­sum is one of the most com­mon and impor­tant min­er­als in the con­struc­tion indus­try and many oth­er indus­tries. Its unique prop­er­ties and wide range of appli­ca­tions make it an indis­pens­able mate­r­i­al for con­struc­tion, med­i­cine, art and agri­cul­ture. Gyp­sum is includ­ed in the list of min­er­als of nation­al impor­tance approved by the Res­o­lu­tion of the Cab­i­net of Min­is­ters of Ukraine dat­ed Decem­ber 12, 1994, No. 827, as an agro­chem­i­cal raw mate­r­i­al, raw mate­r­i­al for fac­ing mate­ri­als (dec­o­ra­tive stones) and cement raw mate­r­i­al.

Conditions of formation and distribution

Gyp­sum is aque­ous cal­ci­um sul­fate (CaSO₄*2H₂O), often asso­ci­at­ed with anhy­drous sul­fate anhy­drite (CaSO₄). In many cas­es, they occur togeth­er in nat­ur­al con­di­tions.

Macro­scop­i­cal­ly, gyp­sum is a lay­ered or mas­sive rock of white col­or and gran­u­lar struc­ture. Depend­ing on the impu­ri­ties, it acquires a light gray, green­ish, yel­low­ish to red and black col­or.

Anhy­drite has a het­ero­ge­neous, but more homo­ge­neous struc­ture than gyp­sum, white col­or with a char­ac­ter­is­tic bluish tint. It dif­fers from gyp­sum in greater den­si­ty and strength. In near-sur­face con­di­tions, in the hyper­ge­n­e­sis zone, anhy­drite hydrates and turns into gyp­sum with an increase in vol­ume.

Mixed — anhy­drite-gyp­sum rocks are quite com­mon. Gyp­sum and anhy­drite are often asso­ci­at­ed with dolomite. Their deposits can also be divid­ed into pri­ma­ry and sec­ondary. Pri­ma­ry for­ma­tion occurs in lagoons and salt lakes dur­ing evap­o­ra­tion of water in hot arid cli­mates. Depend­ing on the com­po­si­tion and tem­per­a­ture of the water, either gyp­sum or anhy­drite pre­cip­i­tates. Sec­ondary accu­mu­la­tions of gyp­sum arise in the process of epi­ge­net­ic trans­for­ma­tion of anhy­drite; most gyp­sum deposits were most like­ly formed in this way.

In semi-desert and desert regions, gyp­sum is often found as veins and veins in the weath­er­ing crust of rocks of var­i­ous com­po­si­tions. It is also formed on lime­stones under the action of waters enriched in sul­fu­ric acid or dis­solved sul­fates. Gyp­sum is also found in oxi­da­tion zones of sul­fide deposits, but not in such large quan­ti­ties as one might expect, due to increased sol­u­bil­i­ty under the action of sul­fu­ric acid. There­fore, gyp­sum is more com­mon in the upper parts of pri­ma­ry ore zones.

Gyp­sum is rel­a­tive­ly rarely found as a typ­i­cal hydrother­mal min­er­al in sul­fide deposits formed at low pres­sures and tem­per­a­tures. In such deposits, it is some­times found as large crys­tals in voids, con­tain­ing inclu­sions of chal­copy­rite, pyrite, spha­lerite and oth­er min­er­als.

Areas of use

The main prop­er­ty that deter­mines the wide­spread use of gyp­sum is its abil­i­ty to par­tial­ly dehy­drate when heat­ed, and after dis­solv­ing in water to hard­en and hard­en in air, turn­ing into stone, due to which it has found wide use in con­struc­tion indus­try.

The most impor­tant areas of appli­ca­tion of gyp­sum and anhy­drite are: pro­duc­tion of gyp­sum binders — build­ing gyp­sum, high-strength gyp­sum, mold­ing gyp­sum, screed gyp­sum, med­ical gyp­sum; pro­duc­tion of cements — gyp­sum slag, anhy­drite, spe­cial, Port­land cement (as an addi­tive); chem­i­cal indus­try — sul­fu­ric acid sul­fate-ammo­ni­um; agri­cul­ture — soil plas­ter­ing, paper indus­try — as a filler.

The vast major­i­ty of gyp­sum raw mate­ri­als extract­ed for the pro­duc­tion of binders are obtained by ther­mal treat­ment of nat­ur­al gyp­sum. The most wide­ly used is build­ing or plas­ter­ing gyp­sum (alabaster), which con­sists main­ly of semi-aque­ous gyp­sum. It is pro­duced by fir­ing gyp­sum stone at a tem­per­a­ture of 107–120º C with sub­se­quent or pre­lim­i­nary grind­ing into a fine pow­der. There are no con­stant con­di­tions for gyp­sum stone for oth­er binders and the suit­abil­i­ty of the raw mate­r­i­al is deter­mined by the qual­i­ty of the final prod­uct.

Gyp­sum screed is pro­duced from gyp­sum or anhy­drite by fir­ing at a tem­per­a­ture of 800‑1000°C with sub­se­quent grind­ing of the result­ing prod­ucts. Hard­ened gyp­sum screed has low ther­mal con­duc­tiv­i­ty, good sound absorp­tion, and high resis­tance to abra­sion. It is used for floor­ing, for brick­work, for the pro­duc­tion of arti­fi­cial mar­ble, etc.

Gyp­sum-slag cement is a hydraulic binder raw mate­r­i­al obtained by the com­bined fine grind­ing of dried gran­u­lat­ed blast fur­nace slag (80–85% by weight), dihy­drate gyp­sum and Port­land cement clink­er. It is used in the con­struc­tion of under­ground and under­wa­ter struc­tures, espe­cial­ly when they are exposed to leach­ing and sul­fate solu­tions.

Anhy­drite cement is a fine­ly ground prod­uct of the fir­ing of dihy­drate gyp­sum at a tem­per­a­ture of 600–700°C or nat­ur­al anhy­drite with var­i­ous addi­tives that acti­vate set­ting. Its areas of appli­ca­tion: the pro­duc­tion of build­ing mor­tars, con­crete, arti­fi­cial mar­ble, hol­low stone.

In its unburnt form, nat­ur­al fine­ly ground gyp­sum has the prop­er­ty of recrys­tal­liza­tion and is used as gyp­sum cement in the con­struc­tion of sin­gle-sto­ry build­ings, cast­ing archi­tec­tur­al details and fin­ish­ing facades of build­ings.

In the process of com­plex pro­duc­tion of sul­fu­ric acid and Port­land cement, dried and dehy­drat­ed gyp­sum or anhy­drite is burned togeth­er with oth­er com­po­nents in a rotary cement kiln until the CaSO₄ is com­plete­ly decom­posed into CaO and SO₃. Sul­fur diox­ide gas is fed to sul­fu­ric acid plants, and the clink­er is ground in the usu­al way to obtain Port­land cement. The pro­duc­tion of ammo­ni­um sul­fate — a valu­able nitro­gen fer­til­iz­er — requires rel­a­tive­ly lit­tle gyp­sum and anhy­drite, which in this case should not con­tain clay impu­ri­ties, which are harm­ful because they com­pli­cate the tech­no­log­i­cal process.

Deposits in Ukraine

Ukraine has sig­nif­i­cant reserves of gyp­sum, espe­cial­ly in the West­ern regions, such as Lviv, Ternopil and Ivano-Frankivsk regions. These deposits pro­vide the coun­try with the nec­es­sary mate­r­i­al for numer­ous indus­tri­al and con­struc­tion needs. The pro­duc­tion of dry­wall, plas­ter and oth­er build­ing mate­ri­als large­ly depends on these local resources, which makes Ukraine an impor­tant play­er in the gyp­sum mar­ket.

The most com­mon in Ukraine are Per­mi­an and Neo­gene deposits. Don­bas ranks first in Ukraine in terms of reserves and pro­duc­tion of gyp­sum and anhy­drite; all explored deposits of raw mate­ri­als for the pro­duc­tion of binders are locat­ed in the Bakhmut dis­trict of Donet­sk region: Mykhailivske (Dekonske), Psheny­chanske, Artemivske, Popas­ni Lisky, Pokrovske, May­orske (Zait­sivske), Vovchynetske, etc.

Gyp­sum reserves at the Artemivske deposit are approved by cat­e­gories in quan­ti­ties: B+C₁ – 147213, includ­ing cat­e­go­ry B – 3954, C₁ – 107671. Cat­e­go­ry C₂ reserves are 28651. In addi­tion, there are reserves in cat­e­gories B+C₁ – 24155 in pro­tec­tive columns. Annu­al gyp­sum pro­duc­tion at the deposit is 25–30 thou­sand tons.

First-grade build­ing gyp­sum can be extract­ed at the Vovchynetske deposit, as well as a mix­ture of gyp­sum and anhy­drite. Although the deposit is not being devel­oped, its gyp­sum reserves are: cat­e­gories A+B+C₁ – 4579, includ­ing cat­e­go­ry A – 588, B – 1677, C₁ – 2314; anhy­drite – A+B+C₁ – 5151, includ­ing cat­e­go­ry A – 592, B – 1817, C₁ – 2742.

Among the pre­vi­ous­ly sur­veyed gyp­sum deposits, which con­sti­tute a poten­tial reserve of this raw mate­r­i­al and can serve as objects for con­duct­ing future explo­ration work, we can name such as Bor­shchagovske, Uhrynivske, Zamyske, Sosulivske, Pered­mis­tevske, etc.

Ukraine has all the oppor­tu­ni­ties for fur­ther devel­op­ment of gyp­sum extrac­tion and pro­cess­ing, which will con­tribute to strength­en­ing the econ­o­my and improv­ing the liv­ing stan­dards of the pop­u­la­tion. Effec­tive use of gyp­sum resources, intro­duc­tion of the lat­est tech­nolo­gies in pro­duc­tion and an envi­ron­men­tal­ly respon­si­ble approach to extrac­tion are the key to sus­tain­able devel­op­ment of this indus­try.