Graphite. Char­ac­ter­is­tics, types, dis­tri­b­u­tion

Ukraine occu­pies an impor­tant place in the world as a sup­pli­er of valu­able min­er­al resources, and graphite is one of them. Due to sig­nif­i­cant reserves of graphite, our coun­try has sig­nif­i­cant poten­tial for the devel­op­ment of the rel­e­vant indus­try. Graphite 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 elec­tri­cal and radio engi­neer­ing raw mate­r­i­al.

So, graphite is a min­er­al of the class of native ele­ments, one of the mod­i­fi­ca­tions of car­bon. It is an allotrop­ic form of car­bon, sim­i­lar to dia­mond, but with a dif­fer­ent crys­tal struc­ture, which gives it unique prop­er­ties, such as low hard­ness, high refrac­tori­ness, elec­tri­cal con­duc­tiv­i­ty, etc. It also com­bines both metal­lic and non-metal­lic prop­er­ties.

Genesis

Graphite is meta­mor­phic and mag­mat­ic in ori­gin, although peg­matite, con­tact-meta­so­mat­ic, and oth­er deposits are also found. Indus­tri­al graphite accu­mu­la­tions are main­ly asso­ci­at­ed with meta­mor­phic deposits. Mag­mat­ic deposits are rare and con­fined main­ly to alka­line and basic rocks.

The fea­si­bil­i­ty of indus­tri­al devel­op­ment of graphite deposits is deter­mined by a num­ber of indi­ca­tors, which deter­mine the amount of costs for min­ing, deposit devel­op­ment, enrich­ment con­di­tions, and there­fore the cost of pro­duc­tion. These include:
— The con­tent of the use­ful com­po­nent in ores and total reserves of the deposit. A high graphite con­tent is the main qual­i­ta­tive indi­ca­tor of the deposit. The yield of con­cen­trate dur­ing enrich­ment depends on the con­tent of graphite in the ore, which, in turn, affects the cost of pro­duc­tion.
— Tech­no­log­i­cal prop­er­ties deter­mined by the struc­tur­al char­ac­ter­is­tics of ores (loose, semi-loose, dense), type of graphite (flaky, dense crys­talline, hid­den crys­talline), etc.

The nature of the ores and the type of graphite are indi­ca­tors that affect the enrich­ment of ores. Ores from graphite deposits in Ukraine are enriched main­ly by flota­tion, which makes it pos­si­ble to enrich ores with a graphite con­tent of 3–5%. At the same time, the flota­tion prop­er­ties of graphite depend on the struc­ture: crys­talline and flaky graphites float eas­i­ly, while cryp­tocrys­talline ones float poor­ly.

The best enriched are flaky ores, in which graphite is in the form of indi­vid­ual crys­tals in the form of scales up to sev­er­al mil­lime­ters in size. Flota­tion of dense crys­talline ores is car­ried out in almost the same way as flaky ones, but at a low­er speed, which is due to the pres­ence in them of a cer­tain amount of cryp­tocrys­talline graphite grains (up to 15–25%), which floats more slow­ly and requires fin­er grind­ing. The type of ores is deter­mined by nat­ur­al fea­tures and depends on the degree of sec­ondary alter­ation of rocks and their min­er­al com­po­si­tion.

To pro­duce high-qual­i­ty graphite, the raw mate­r­i­al is sub­ject­ed to heat treat­ment.

Areas of use

The use of graphite in var­i­ous indus­tries is due to its unique prop­er­ties: due to its high melt­ing point, it is used in met­al­lur­gy for the man­u­fac­ture of refrac­to­ry cru­cibles and paints, foundry molds; due to its high elec­tri­cal con­duc­tiv­i­ty and chem­i­cal sta­bil­i­ty, in elec­tri­cal engi­neer­ing for the pro­duc­tion of gal­van­ic cells, alka­line bat­ter­ies, etc.; due to its low coef­fi­cient of fric­tion, it is used as a lubri­cant, for the man­u­fac­ture of antifric­tion prod­ucts; fine­ly ground fat­ty graphites are used for the man­u­fac­ture of pen­cil rods, paints, and copy paper; graphite is also wide­ly used in nuclear tech­nol­o­gy as a mod­er­a­tor of nuclear reac­tions, in jet tech­nol­o­gy for coat­ing rock­et engine noz­zles, com­bus­tion cham­bers, and nose cones.

Today, the use of arti­fi­cial graphite is increas­ing, includ­ing that which crys­tal­lizes from cast iron after its pour­ing or is obtained by heat­ing coal to 2200–2500° using the Achesov method. It is used for the man­u­fac­ture of elec­trodes, refrac­to­ry prod­ucts, in par­tic­u­lar in rock­et tech­nol­o­gy, for nuclear reac­tors.

Con­sumer require­ments for com­mod­i­ty graphite are very diverse and can vary both for dif­fer­ent types of raw mate­ri­als and for dif­fer­ent deposits.

There are no approved require­ments for raw graphite ores. Ores with a con­tent of 2.3–2.4% of clear­ly crys­talline graphite are mined by the open method, although lean­er ores can also be enriched, which leads to an increase in the cost of pro­duc­tion. At the same time, dense crys­talline graphites, which are used pri­mar­i­ly in foundry pro­duc­tion, are poor­ly enriched, so their con­tent in ores should exceed 60–70%, less rich ores are rarely mined.

Deposits in Ukraine

Ukraine is one of the lead­ing coun­tries in the world in terms of the num­ber of deposits and dis­cov­ered reserves. Graphite min­er­al­iza­tion in Ukraine is asso­ci­at­ed with the struc­tures of the Ukrain­ian Crys­talline Shield (UCS), with­in which four graphite-bear­ing areas are dis­tin­guished: Pobuzsky, Kirovo­grad­sky, Prya­zovsky and Volyn­sky. In total, there are about 100 deposits and ore occur­rences of meta­mor­phic graphite in this ter­ri­to­ry. Only one of them is being devel­oped — Zavalivske.

Graphite-bear­ing rocks form lay­ered and lentic­u­lar bod­ies with a thick­ness of 300 m; their length is from 500 to 1500 m, occa­sion­al­ly up to 3.5–5.0 km. The depth of graphite ores is from 10 to 80 m. Graphite-like sub­stance is also found in the form of small lens- and nest-like accu­mu­la­tions and thin lay­ers among pre-Meso­zoic shales and car­bon­ate rocks, as well as in a scat­tered form in the rocks them­selves, main­ly in quartzites, of the Chyvchyn and Rakhiv mas­sifs (Carpathi­ans).

The Zavalivske deposit in the Pobuz dis­trict of the Kirovo­grad region is a typ­i­cal exam­ple of the USh deposits, which are con­fined to the mid­dle reach­es of the South­ern Bug. About 40 lay­er-like bod­ies with a thick­ness of 3.5 to 80 m are dis­tin­guished in the deposit. Graphite even­ly pen­e­trates the rock in the form of scales 2–4 mm in size, its con­tent is 6–10%, rarely 14–20%. Most­ly weath­ered, kaoli­tized ores are devel­oped. The total reserves of graphite ore in the deposit are 112,087 thou­sand tons, con­firmed — 96,647 thou­sand tons. graphite, respec­tive­ly 6902.9 and 6132.4 thou­sand tons.

A sim­i­lar Zarichne graphite deposit has been explored along with the Zavalivske deposit, as well as the rel­a­tive­ly small Piv­den­ny-Khaschu­vatske and Demovyarske deposits.

The largest after Zavalivske is the Petrivske deposit in the Kryvyi Rih dis­trict of the Kirovohrad region. Graphite-bear­ing deposits are con­fined to the con­tact of crys­talline lime­stones, which are over­lain by biotite-pla­gio­clase gneiss­es and bro­ken by gray gran­ites of the Ingulet­sk com­plex. The graphite con­tent varies from 2–5 mm, although fine-grained graphite pre­dom­i­nates. In the upper part, graphite ores are kaolin­i­tized, trans­formed into loose graphite clays with a graphite con­tent of 1.3 to 6%. The pro­ject­ed resources of the deposit are 21 mil­lion tons of ore with a graphite con­tent of 8.7–9.0%. Con­firmed graphite reserves at the deposit are 540 thou­sand tons.

Graphite ores of the Petrivske deposit are main­ly fine-grained and are divid­ed into the fol­low­ing types:

• Kaolin­ized graphite schists, trans­formed into graphite-kaolin rocks, which are cal­ci­t­ized on the sur­face, and in some areas quartz­ized and sili­ci­fied.
• Graphi­tized biotite gneiss­es, main­ly kaolin­ized.
• Dense graphite schists.

The most wide­spread are weath­ered graphite schists, trans­formed into graphite-kaolin rocks of dark gray col­or with a bluish tint.

The Bur­tyn deposit of Khmel­nyt­skyi region is locat­ed in the strip of devel­op­ment of graphite-bear­ing gneiss­es up to 18 km long. Its reserves on the ter­ri­to­ry of 1.7 km² with an ore deposit thick­ness of 49 m are esti­mat­ed at about 100 mil­lion tons, and the fore­cast resources to a depth of 150 m are 340 mil­lion tons of ore. The aver­age graphite con­tent is 6.7%. The ore is eas­i­ly enriched and the yield of con­cen­trate with clear­ly crys­talline flake graphite is 90–95%. The deposit can be devel­oped in an open pit (depth of occur­rence 14–20 m), but is locat­ed on arable land.

The ores of the Bur­tyn graphite deposit are close in chem­i­cal com­po­si­tion to the ores of Zaval­ly. The ores have a rel­a­tive­ly high con­tent of sul­fide sul­fur, oxide and iron oxide, which is asso­ci­at­ed with the pres­ence of a larg­er num­ber of sul­fide min­er­als. The rock-form­ing min­er­als of the ores in both deposits are quite sim­i­lar. At the same time, the Zavaliv deposit con­tains a sig­nif­i­cant amount of gar­net (20%), as well as a notice­ably high­er con­tent of sul­fides (2–7%) com­pared to the Bur­tyn deposit.

The graphite indus­try of Ukraine has sig­nif­i­cant poten­tial for devel­op­ment, giv­en the avail­able nat­ur­al resources. The use of Ukrain­ian graphite in var­i­ous indus­tries, from tra­di­tion­al met­al­lur­gy to cut­ting-edge tech­nolo­gies, is a tes­ta­ment to its high qual­i­ty. Thanks to its unique prop­er­ties, graphite will con­tin­ue to play a key role in mod­ern tech­nol­o­gy and sci­ence.