Phl­o­go­pite is a com­mon min­er­al of the sil­i­cate class, a sub­class of sheet sil­i­cates. A type of biotite with a mag­ne­sium com­po­si­tion. The col­or is yel­low, dark brown or red-brown. It is some­times called “brown mica”. Phl­o­go­pite crys­tals are colum­nar, short-pris­mat­ic, lamel­lar.

The first men­tion of phl­o­go­pite dates back to the mid­dle of the 19th cen­tu­ry and is asso­ci­at­ed with the name of the min­er­al­o­gist Johann Bre­i­thaus, who gave the min­er­al such an unusu­al name, which trans­lates as “fiery”.

Phl­o­go­piteis 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 elec­tri­cal and radio-tech­ni­cal raw mate­ri­als.

Genesis

Phl­o­go­pite occurs in con­tact-meta­so­mat­ic for­ma­tions and in peg­matite veins that cross through dolomi­tized lime­stones or oth­er sil­i­ca-poor and iron-mag­ne­sium rocks; in ultra­ba­sic rocks such as kim­ber­lites, peri­dotites, lam­proites, and ser­pen­tinites; and in meta­mor­phic rocks.

Phl­o­go­pite deposits are of hydrother­mal-meta­so­mat­ic ori­gin and are formed by the con­tact of mag­ne­sium rocks (hyper­b­a­sites, dolomites, and oth­ers) with alu­mi­nosil­i­ca rocks (gneiss, pegamites, alka­line mag­matites). It is also pro­duced arti­fi­cial­ly: by crys­tal­liza­tion from the melt. Asso­ci­at­ed min­er­als include apatite, cal­cite, dolomite, mag­netite, diop­side, spinel, nepheline. It is also found in ultra­maf­ic rocks — such as kim­ber­lites, peri­dotites, lam­proites and ser­pen­tinites. Also known in meta­mor­phic rocks.

The devel­op­ment of deposits is car­ried out by open pit and mine meth­ods. Large crys­tals are mined for tech­ni­cal and dec­o­ra­tive needs. Small mass­es and waste are crushed, enriched and used as a filler or insu­la­tor.

Distribution of phlogopite

The min­er­al is found in con­tact-meta­mor­phosed or meta­so­mat­ic mar­bles of Val Malenko (Italy), Adr­gu­ra (Great Britain), Pyre­nees (France), Car­ling­ford (Ire­land), Iron Hill (pcs. Col­orado, USA), in the Azov region (Ukraine). It is found in kim­ber­lites (in South Africa, Cana­da), car­bon­atites (Kov­dor, Rus­sia).

In Ukraine, phl­o­go­pite is present with­in the Ukrain­ian Shield, par­tic­u­lar­ly in the Vin­nyt­sia region (Lukashiv­ske deposit). Phl­o­go­pite from some deposits is con­sid­ered a poten­tial source of rare met­als.

The glob­al mar­ket for phl­o­go­pite is small­er than that of mus­covite, but it is valu­able in high-tem­per­a­ture tech­nolo­gies. The largest pro­duc­ers are Cana­da, Rus­sia, India, and Fin­land.

Phlogopite deposits in Ukraine

The Lukashiv­ske deposit of phl­o­go­pite is locat­ed near the vil­lage of Lukashiv­ka, Lytyn dis­trict, Vin­nyt­sia region. Phl­o­go­pite deposits are esti­mat­ed at 30 mil­lion tons. The mica con­tent of the ore ranges from 15–40 to 80 %. Phl­o­go­pite is char­ac­ter­ized by a very low iron oxide con­tent of 0.36–1.7%.

The speci­fici­ty of ores also lies in their com­po­si­tion — mica plates, most­ly from 2–3 to 5–10 mm in size, are placed in mar­ble-like rock com­posed main­ly of cal­cite. Some of the ores are rep­re­sent­ed by phl­o­go­pi­tites con­tain­ing up to 80% mica.

The min­i­mum depth of phl­o­go­pite ores is about 40 m. Over­bur­den is most­ly clay. The thick­ness of ore bod­ies exceeds 50 m. In wells, they are traced to a depth of 300 m.

Practical significance

Phl­o­go­pite is an inex­pen­sive min­er­al, and its main appli­ca­tion is found in indus­tri­al and jew­el­ry fields.

It is used as an addi­tive in the pro­duc­tion of cement mix­tures, fire-resis­tant paints and var­nish­es, paper, heat-insu­lat­ing mate­ri­als, explo­sives, in the pro­duc­tion of ceram­ics, as well as in the pro­cess­ing of fur­ni­ture, table­ware, cab­i­nets and var­i­ous acces­sories.

In the jew­el­ry indus­try, the min­er­al is used less often due to the com­plex­i­ty of pro­cess­ing. It can be eas­i­ly split, so those jew­el­ers who work with the min­er­al treat it with caul­dron, cut­ting the min­er­al in lay­ers. So the inserts become stronger, and the cut plates of sali­va sparkle and resem­ble small galax­ies.

Most often, a leather or met­al frame is cho­sen for the stone, some­times in com­bi­na­tion with oth­er inex­pen­sive min­er­als.