Chalk is a sed­i­men­ta­ry, bio­genic, weak­ly cement­ed, fine-grained car­bon­ate rock. It is com­posed main­ly of cal­citic remains of marine plank­ton­ic algae—coccolithophores. It forms at depths of over 100–300 m in warm seas as a result of the accu­mu­la­tion of organ­ic remains (pri­mar­i­ly shells) and the pre­cip­i­ta­tion of CaCO₃ from sea­wa­ter. The for­ma­tion of chalk occurred main­ly dur­ing the Meso­zoic era, specif­i­cal­ly in the Cre­ta­ceous peri­od, which last­ed from about 145 to 66 mil­lion years ago. Dur­ing this time, large areas of the present-day con­ti­nents were cov­ered by warm shal­low seas, where inten­sive accu­mu­la­tion of organ­ic mate­r­i­al took place.

Chalk has a homo­ge­neous fine-grained struc­ture, usu­al­ly white or light grey in col­or, some­times with admix­tures of clay, quartz, phos­phates, or organ­ic mat­ter that give it dif­fer­ent shades. The main min­er­al com­po­nent of the rock is cal­cite (CaCO₃), which makes up to 98% of its mass. Due to its high poros­i­ty (some­times over 40%) and low den­si­ty (approx­i­mate­ly 1.5–2.6 g/cm³), chalk has low hard­ness (1–2 on the Mohs scale), crum­bles eas­i­ly, leaves a mark on sur­faces, absorbs water well, and reacts active­ly with acids with the release of car­bon diox­ide.

Chalk 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, cement raw mate­r­i­al, and raw mate­r­i­al for build­ing stone and crushed stone.

Chalk is usu­al­ly extract­ed by open-pit (quar­ry) min­ing. The extract­ed blocks are crushed and placed in water. Dur­ing mix­ing, cal­ci­um par­ti­cles float to the sur­face. They are then dried and used for var­i­ous pur­pos­es. Unprocessed stone is sent for cal­ci­na­tion to pro­duce lime.

The belt of Cre­ta­ceous deposits extends from the Mugodzhary in west­ern Kaza­khstan through Russ­ian regions (Bel­go­rod, Voronezh, Vol­gograd, Sara­tov oblasts) into Ukraine, Poland, Ger­many, France, and Great Britain.

In Ukraine, there are about 60 deposits with total bal­ance reserves of approx­i­mate­ly 450 mil­lion tons. The main reserves are con­cen­trat­ed in the Donet­sk region — 218 mil­lion tons. The thick­ness of chalk stra­ta in west­ern regions reach­es up to 20 m, while in east­ern regions it is 50–56.5 m. Major reserves are locat­ed near the cities of Slo­vian­sk (Donet­sk region), Izium (Kharkiv region), Lysy­chan­sk (Luhan­sk region), Hlukhiv (Sumy region), and Novhorod-Siver­skyi (Cherni­hiv region). Deposits are also known in Volyn, Rivne, and Ternopil regions.

One of the most well-known chalk extrac­tion sites is the Tor­govytske deposit. It is locat­ed 17 km from the urban-type set­tle­ment of Mlyniv in the vil­lage of Tor­govyt­sia, Rivne region. Chalk from the Mlyniv area is char­ac­ter­ized by its envi­ron­men­tal puri­ty and high cal­ci­um con­tent (98.5–99.39%) and con­tains almost no impu­ri­ties. Such pure chalk was used for feed pro­duc­tion or giv­en direct­ly to ani­mals. Only one deposit in Ukraine, near Slo­vian­sk, pro­duces raw mate­r­i­al with sim­i­lar prop­er­ties.

The com­pa­ny “ViP-AKVAREL” was engaged in chalk extrac­tion at this deposit. It car­ried out the full pro­duc­tion cycle, from quar­ry extrac­tion to pro­cess­ing at its facil­i­ties and final pack­ag­ing. The com­pa­ny spe­cial­ized in pro­duc­ing puri­fied chalk, feed-grade chalk, and chalk for soil lim­ing.

Anoth­er high-qual­i­ty chalk deposit was dis­cov­ered near the city of Zdol­buniv in the Rivne region in the 1870s. How­ev­er, accord­ing to some sources, locals had known about chalk in the area long before that and extrac­tion began ear­li­er than the 1870s. Min­ing at the Zdol­buniv deposit is car­ried out by open-pit meth­ods. The main con­sumer is the State Enter­prise “Zdol­buniv cement and slate plant,” which uses local raw mate­r­i­al for cement pro­duc­tion.

Chalk has high puri­ty (up to 98% cal­ci­um car­bon­ate), mak­ing it suit­able for the pro­duc­tion of cement, lime, min­er­al addi­tives, paper, and plas­tics. Clay inter­lay­ers are often present in the deposit and also have indus­tri­al sig­nif­i­cance. The bal­ance reserves of the Zdol­buniv deposit (hydraulic dump area) are: loams — 5,928 thou­sand tons; chalk — 18,700 thou­sand tons, includ­ing 17,408 thou­sand tons of dry and 1,292 thou­sand tons of water-sat­u­rat­ed mate­r­i­al. Annu­al pro­duc­tion capac­i­ty is esti­mat­ed at: loams — 402.7 thou­sand tons; chalk — 1,306.5 thou­sand tons.

Chalk is used in agri­cul­ture, the paper and rub­ber indus­tries, con­struc­tion, and oth­er sec­tors.

• The min­er­al is includ­ed in the com­po­si­tion of cement mix­tures when it is nec­es­sary to give them soft­ness.
• In the pro­duc­tion of glass, paint and var­nish mate­ri­als, rub­ber, plas­tic mass­es, rub­ber, when cre­at­ing com­pos­ite mate­ri­als based on PVC.
• Chalk is active­ly used in the pro­duc­tion of car­pets and linoleum. Chalk helps reg­u­late the vis­cous prop­er­ties of latex glue, give prod­ucts strength and improve heat-sav­ing prop­er­ties.
• Chalk is also used in the pro­duc­tion of com­pound feed and soil fer­til­iz­ers.
• The paper and card­board indus­try can­not do with­out chalk.

Chalk is a valu­able nat­ur­al raw mate­r­i­al with a high cal­ci­um con­tent, wide­ly used in indus­try, agri­cul­ture, and con­struc­tion. In Ukraine, there are numer­ous high-qual­i­ty chalk deposits, par­tic­u­lar­ly in the Rivne and Donet­sk regions, which ensure domes­tic demand and export poten­tial.