Pyro­phyl­lite is an impor­tant raw mate­r­i­al for many indus­tries due to its unique phys­i­cal and chem­i­cal prop­er­ties. Demand for pyro­phyl­lite is dri­ven by its chem­i­cal inert­ness, strength, and abil­i­ty to with­stand ther­mal shock.

Pyro­phyl­lite 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 and raw mate­r­i­al for elec­tri­cal and radio engi­neer­ing.

General information

Pyro­phyl­lite is a lay­ered sil­i­cate with the chem­i­cal for­mu­la Al₂[Si₄O₁₀](OH)₂. In the com­po­si­tion of this min­er­al, alu­minum can be par­tial­ly replaced by mag­ne­sium and iron, and cal­ci­um, sodi­um, potas­si­um, and tita­ni­um often act as impu­ri­ties.

It occurs in the form of lamel­lar, thin-plat­ed, radi­al­ly-rayed, and gran­u­lar aggre­gates. Some of its cryp­tocrys­talline vari­eties are known as agal­ma­toite, fig­ure stone, or pagodite. The col­or of the min­er­al varies from white to green­ish, yel­low­ish, or brown­ish. Pyro­phyl­lite has a glassy lus­ter with a pearly sheen on cleav­age planes, a hard­ness of 1–2 on the Mohs scale, a den­si­ty of 2650 to 2900 kg/m³ and a melt­ing point of about 1700°C.

Pyro­phyl­lite is formed as a result of sil­i­cate hydrol­y­sis dur­ing the process of par­a­ge­net­ic trans­for­ma­tions, dur­ing the for­ma­tion of sec­ondary quartzites, as well as through the dehy­dra­tion of clay min­er­als dur­ing low-tem­per­a­ture meta­mor­phism. The min­er­al is easy to process, crushed into a white pow­der, chem­i­cal­ly inert, and has the abil­i­ty to retain cer­tain active chem­i­cals on its sur­face. It has prop­er­ties such as slip­per­i­ness, soft­ness, oili­ness, and stick­i­ness. After heat treat­ment, pyro­phyl­lite forms a dense and durable white shale with low mois­ture capac­i­ty, insignif­i­cant shrink­age, and high chem­i­cal resis­tance. It has good resis­tance to ther­mal shock, low ther­mal expan­sion, and good ther­mal and elec­tri­cal insu­la­tion prop­er­ties.

Pyrophyllite deposits in Ukraine

In Ukraine, pyro­phyl­lite shale deposits are known to exist in the Zhy­to­myr region, in the north-west of the Ukrain­ian Shield (U.S.), par­tic­u­lar­ly with­in the Ovruch series (Nago­ri­anske, Zbrankivske, and Kuri­an­ivske deposits). The Shyshalivs­ka area is also promis­ing, with esti­mat­ed resources of approx­i­mate­ly 0.05 mil­lion tons. Pyro­phyl­lite deposits are usu­al­ly con­fined to crys­talline shale stra­ta asso­ci­at­ed with quartzites. Pro­duc­tive lay­ers are 1.6 to 2 meters thick, and the con­di­tion lay­ers in the mid­dle part of the deposit are 0.5 to 0.9 meters thick.

The Nago­ryanske deposit is locat­ed 2 km north of the vil­lage of Nago­ryany in the Ovruch dis­trict of Zhy­to­myr region. Pyro­phyl­lite shales occur among pink quartzites of the Tovkachivs­ka For­ma­tion of the Ovruch Series of the Pro­tero­zoic peri­od, form­ing lens­es and lay­ers with a thick­ness of 0.1 to 40 meters. Depend­ing on the col­or, struc­ture, tex­ture, and min­er­al com­po­si­tion, the fol­low­ing types of schist are dis­tin­guished: pink greasy, lilac slight­ly sandy, heav­i­ly sandy, and quartz-pyro­phyl­lite with a high quartz con­tent. The main part is made up of pink greasy and lilac slight­ly sandy shales. The total proven reserves of the deposit amount to 1,916 thou­sand tons. Shale and quartzite for met­al­lur­gi­cal pur­pos­es are extract­ed man­u­al­ly in an open pit on an episod­ic basis.

The Zbranky deposit is locat­ed 1.5 km north of the vil­lage of Zbranky in the Ovruch dis­trict. Its rocks are rep­re­sent­ed by quartzites and sand­stones of the Tovkachivs­ka For­ma­tion of the Ovruch Series, which con­tain lay­ers of pyro­phyl­lite shale with a thick­ness of 0.1 to 1.5 meters. Total shale reserves are esti­mat­ed at 31,500 tons. Extrac­tion was car­ried out by min­ing. Shale is used to man­u­fac­ture bea­con and soot burn­ers, and waste is used in ceram­ic pro­duc­tion.

The Kuryanivske deposit is also locat­ed in the Ovruch dis­trict of Zhy­to­myr region and is locat­ed in the con­tact zone between the effu­sive rocks of the Zbrankivs­ka For­ma­tion and the quartzites of the Tovkach For­ma­tion. It con­tains a lay­er of pyro­phyl­lite shale with a thick­ness of 0.7 to 1.9 meters (aver­age 1.3 m). The roof of the lay­er lies at a depth of 10.9 to 90.5 meters. The host rocks are pink fine-grained quartzites. The total reserves of the deposit are esti­mat­ed at 346 thou­sand tons, and the pro­ject­ed resources at 279.1 thou­sand tons. A mine has been pre­pared for the exploita­tion of the deposit on the basis of OJSC “Kvart­samotsvi­ti”.

Areas of application

Pyro­phyl­lite is wide­ly used in the pro­duc­tion of high­ly refrac­to­ry ceram­ic prod­ucts. It is used as a filler in the paper and rub­ber indus­tries, in the pro­duc­tion of lubri­cants, pen­cil leads, and as a gem­stone (agal­ma­toite). It is used as a gas­ket for heat­ing ele­ments in elec­tric fur­naces.

In the US, pyro­phyl­lite is used to make spe­cial oil paints for cam­ou­flag­ing mil­i­tary equip­ment and ships. It is used in the per­fume and phar­ma­ceu­ti­cal indus­tries to make pow­der and tooth­paste, in the con­fec­tionery indus­try to sprin­kle and pol­ish can­dies, and in the pro­duc­tion of cable rub­ber and bat­tery box­es. It is used to make ceram­ic prod­ucts, roof­ing mate­ri­als, elec­tri­cal porce­lain, lamp sock­ets, tips for weld­ing equip­ment, as well as refrac­to­ry bricks, cement, and con­crete.

Pyro­phyl­lite is an impor­tant min­er­al with a wide range of appli­ca­tions in var­i­ous indus­tries. Ukraine has sig­nif­i­cant prospects for devel­op­ing the extrac­tion of this min­er­al thanks to its exist­ing deposits. The ratio­nal devel­op­ment of pyro­phyl­lite resources can sig­nif­i­cant­ly increase the coun­try’s eco­nom­ic poten­tial in the pro­duc­tion of refrac­to­ry, elec­tri­cal, and ceram­ic mate­ri­als.