Mar­shal­lite is a loose or weak­ly con­sol­i­dat­ed rock com­posed of 85–98% fine quartz grains and var­i­ous impu­ri­ties. It is a resid­ual prod­uct of the weath­er­ing of sili­ci­fied lime­stones, quartzites, and some oth­er siliceous rocks. Mar­shal­lite is also known as quartz dust or flour quartz.

It forms through the crush­ing and screen­ing of quartz material.In terms of chem­i­cal com­po­si­tion, mar­shal­lite main­ly con­sists of SiO₂, with minor impu­ri­ties of Al₂O₃, Fe₂O₃, and TiO₂. It has an amor­phous or crys­talline struc­ture with a pow­dery frac­tion, white, gray­ish, or translu­cent-milky col­or, a Mohs hard­ness of 7, and high resis­tance to ther­mal and chem­i­cal influ­ences.

Mar­shal­lite 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 an abra­sive raw mate­r­i­al.

Conditions of formation and extraction

Mar­shal­lite forms through sev­er­al geo­log­i­cal process­es. The main fac­tors include hydrother­mal activ­i­ty, dur­ing which sil­i­ca-rich hot solu­tions pen­e­trate rocks and deposit quartz in the form of fine, dust-like mass­es; mechan­i­cal break­down of quartz rocks dur­ing weath­er­ing or quar­ry­ing; and sed­i­men­ta­ry process­es, when quartz dust set­tles in marine or fresh­wa­ter basins and becomes com­pact­ed into thin lay­ers. These for­ma­tion con­di­tions give the min­er­al high puri­ty and homo­gene­ity, which are impor­tant for indus­tri­al use.

Mar­shal­lite is main­ly extract­ed by open-pit min­ing. The quar­ry­ing method involves the devel­op­ment of quartz sands, their crush­ing, and screen­ing to obtain a fine pow­der frac­tion. Addi­tion­al indus­tri­al pro­cess­ing includes clas­si­fi­ca­tion, wash­ing, dry­ing, and grind­ing to the required par­ti­cle size. Glob­al pro­duc­tion reach­es mil­lions of tons per year, depend­ing on demand from the glass and abra­sive indus­tries.

Quartz dust dur­ing extrac­tion can cause res­pi­ra­to­ry dis­eases such as sil­i­co­sis among work­ers, while quar­ry­ing sig­nif­i­cant­ly alters land­scapes and affects soils, hydro­log­i­cal regimes, flo­ra, and fau­na. To min­i­mize neg­a­tive impacts, dust con­trol sys­tems, quar­ry recla­ma­tion, and emis­sion mon­i­tor­ing are applied.

Occurrences and deposits in Ukraine

Occur­rences of mar­shal­lite in Ukraine have been record­ed in the Kryvyi Rih iron ore basin, where they are asso­ci­at­ed with hyper­gene zones of siliceous–iron and schistose–siliceous–iron for­ma­tions, par­tic­u­lar­ly oxi­dized ores of the Sak­sa­han dis­trict. Anoth­er sig­nif­i­cant deposit is locat­ed north­west of Kyiv — the Havrylivske deposit (near the vil­lage of Havryliv­ka, Dymer dis­trict). It is rep­re­sent­ed by a bed enriched with mar­shal­lite, with an out­crop area of about 130 hectares, a thick­ness of 1.4–4.8 m, and a depth of occur­rence of 5.12–8.75 m, asso­ci­at­ed with Polta­va sands.

The min­er­al com­po­si­tion of the deposit is dom­i­nat­ed by quartz (93–94%) and kaoli­n­ite (5–6%), with minor amounts of pla­gio­clase, chal­cedony, leu­cox­ene, and traces of tour­ma­line, rutile, dis­thene, zir­con, apatite, ilmenite, and epi­dote. The gran­u­lo­met­ric com­po­si­tion is dom­i­nat­ed by a fine frac­tion of 0.01–0.06 mm (96–98%). The over­bur­den thick­ness is 7.1 m, half of which is high-qual­i­ty brick and tile raw mate­r­i­al. Esti­mat­ed reserves of mar­shal­lite are about 5.4 mil­lion m³.

Out­side Ukraine, mar­shal­lite is also found in the Unit­ed States, Chile, South Africa, and Asia, with sev­er­al iso­lat­ed occur­rences in Europe.

Uses of marshallite

Mar­shal­lite is wide­ly used in indus­try for the pro­duc­tion of liq­uid glass, which serves as a base for man­u­fac­tur­ing arti­fi­cial stone, build­ing com­po­nents (in com­bi­na­tion with blast-fur­nace slag, sand, saw­dust, etc.), as well as artis­tic and dec­o­ra­tive prod­ucts made from ground marble.It is used for den­si­fy­ing porous stone mass­es, accel­er­at­ing cement hard­en­ing, soil sta­bi­liza­tion, impreg­na­tion of road sur­faces, coal bri­quet­ting, pro­duc­tion of acid-resis­tant cement, abra­sive mate­ri­als, refrac­to­ry prod­ucts, and arc lamp cores. In addi­tion, mar­shal­lite is a raw mate­r­i­al for the pro­duc­tion of sil­i­cate adhe­sives, ply­wood, fiber­board, sur­gi­cal dress­ings, and is also used as a filler in the plas­tics, rub­ber, glass, and porcelain–faience indus­tries.