Per­lite. Prop­er­ties, uses, and deposits in Ukraine

Per­lite is an acidic, water-bear­ing vol­canic glass with a char­ac­ter­is­tic spher­i­cal struc­ture that allows it to break into small balls with an iri­des­cent sur­face sim­i­lar to pearls. It belongs to the group of acidic vol­canic glass along with obsid­i­an and pech­stein, but the lat­ter are not found in Ukraine.

Per­lite 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 raw mate­r­i­al for petro­le­um surgery and for light­weight con­crete fillers.

Properties of perlite

The main fea­ture of per­lite, which ensures its indus­tri­al use, is its abil­i­ty to expand when heat­ed to 900‑1200°C, increas­ing its vol­ume by 5–20 times. Expand­ed per­lite sand is a light­weight and porous mate­r­i­al with a bulk den­si­ty of 50–600 kg/m³, which is used in many indus­tries and agri­cul­ture.

Per­lite is formed as a result of the hydra­tion of vol­canic glass. This process can occur direct­ly dur­ing the cool­ing of vol­canic bod­ies due to the redis­tri­b­u­tion of water in them under the influ­ence of tem­per­a­ture and pres­sure changes, which caus­es the for­ma­tion of pri­ma­ry per­lite. Sec­ondary per­lite is formed lat­er, under the action of hydrother­mal solu­tions or sur­face waters.

Per­lite can have dif­fer­ent tex­tures, which can be porous or mas­sive. Its com­po­si­tion includes water exceed­ing 1.5%, as well as min­er­al inclu­sions and micro­lites, in par­tic­u­lar quartz, feldspar, pla­gio­clase, biotite, and amphi­bole. The rock also con­tains spherulites, which are aggre­gates of cal­ci­nat­ed feldspar and sil­i­ca mod­i­fi­ca­tions, as well as sec­ondary min­er­als such as zeo­lites and mont­mo­ril­lonite.

The chem­i­cal com­po­si­tion of per­lite varies, but typ­i­cal­ly con­tains 68–76% sil­i­con diox­ide (SiO₂), 1–14% alu­minum oxide (Al₂O₃), 0.4–1.5% iron oxides (Fe₂O₃ and FeO), 0.5–1.5% cal­ci­um oxide (CaO), 2–4% sodi­um oxide (Na₂O) and potas­si­um oxide (K₂O), and up to 9% bound water (H₂O⁺).

Per­lite has a den­si­ty of 2.30–2.39 g/cm³, and its poros­i­ty can range from 1.8% to 70%, which makes this rock unique in terms of its phys­i­cal and chem­i­cal prop­er­ties.

Perlite deposits in Ukraine

Per­lite deposits are usu­al­ly con­fined to areas of Pale­o­gene-Qua­ter­nary vol­can­ism. In Ukraine, they are locat­ed with­in the Bere­hove dis­trict of the Zakarpat­tia region, where they are asso­ci­at­ed with the vol­canic for­ma­tions of the Vygor­lat-Gutyin­sky range. The main deposits are Shi­no-Var­na, Roko­sivske, Fogorske, and Ardi­vske, with proven reserves of 50,700 thou­sand m³.

The Ardi­vske deposit is locat­ed 3 km south­east of the Bere­hove rail­way sta­tion on arable land on the north­ern out­skirts of the city of Bere­hove. The area of the site is 23.7 hectares. The deposit con­sists of sed­i­men­ta­ry and vol­canogenic for­ma­tions of the Tor­ton and Sar­ma­t­ian peri­ods, which form a large gen­tle anti­cli­nal fold. Per­lite occurs in two main areas — Ardi­vske and Zatish­ni­anske, which were formed as a result of the activ­i­ty of the Ardiv vol­cano.

Geo­log­i­cal work at the Ardi­vskyi deposit was car­ried out in 1959–1961. The main raw mate­r­i­al — expand­ed per­lite sand — has a bulk den­si­ty of 150–180 kg/m³, which meets the require­ments of tech­ni­cal stan­dards. The total reserves of per­lite in the Ardi­vskyi area in cat­e­gories A, B, and C1 amount to 9,336 thou­sand m³, of which the bal­ance resources are record­ed in the amount of 1,180 thou­sand m³ (cat­e­go­ry A), 4,256 thou­sand m³ (cat­e­go­ry B), and 3,900 thou­sand m³ (cat­e­go­ry C₁). In the Zatish­nyan­sky sec­tion of the Ardi­vsky deposit, in addi­tion to per­lite rocks, cov­er clays suit­able for the pro­duc­tion of hol­low blocks, tiles, and oth­er build­ing mate­ri­als were stud­ied.

Per­lite is also mined at the Rokosovsky deposit, locat­ed north of the vil­lage of Rokoso­vo. Rio-dacite tuffs with a thick­ness of up to 50 m are a use­ful min­er­al resource.

Use of perlite

Per­lite is pri­mar­i­ly used as a raw mate­r­i­al in petro­le­um and for light­weight con­crete fillers, play­ing an impor­tant role in the con­struc­tion indus­try. It is used to cre­ate high-qual­i­ty build­ing mate­ri­als that pro­vide strength, dura­bil­i­ty, and weight reduc­tion in struc­tures. The basis of such raw mate­ri­als is nat­ur­al min­er­als and rocks that under­go spe­cial pro­cess­ing in order to achieve the nec­es­sary char­ac­ter­is­tics.

Expand­ed per­lite gives con­crete low den­si­ty, high heat and sound insu­la­tion, and also improves its fire resis­tance. Such con­crete is used in the con­struc­tion of both res­i­den­tial and indus­tri­al facil­i­ties, espe­cial­ly in con­di­tions of increased ener­gy effi­cien­cy require­ments.

Per­lite is wide­ly used in the con­struc­tion indus­try due to its unique prop­er­ties, such as non-com­bustibil­i­ty, low water absorp­tion, and sound and heat insu­la­tion char­ac­ter­is­tics. Per­lite sand is used to pro­duce light­weight con­crete, plas­ter solu­tions, per­lite prod­ucts based on syn­thet­ic binders, gyp­sum and sil­i­cate-per­lite mate­ri­als. Expand­ed per­lite is a raw mate­r­i­al for the man­u­fac­ture of ther­mal insu­la­tion mate­ri­als, such as per­lite-phos­phate slabs, bricks, shaped prod­ucts, per­lite pow­ders for low-tem­per­a­ture insu­la­tion, and oth­er insu­la­tion prod­ucts.

In met­al­lur­gy, per­lite-graphite mix­tures are used to coat steel cast­ing con­tain­ers. In agri­cul­ture, expand­ed per­lite is used to improve soil struc­ture, retain mois­ture, cre­ate a sta­ble pH envi­ron­ment, and as a car­ri­er for pes­ti­cides. In addi­tion, per­lite sand is an effec­tive fil­ter­ing mate­r­i­al for puri­fy­ing water, syrups, oils, beer, and phar­ma­ceu­ti­cals.