Flu­o­rite. Char­ac­ter­is­tics, prop­er­ties, dis­tri­b­u­tion

Fluorspar, also known as flu­o­rite (CaF₂), is one of the most com­mon min­er­als active­ly used in var­i­ous indus­tries. Its name comes from the Latin word “fluere,” mean­ing “to flow,” as this min­er­al low­ers the melt­ing tem­per­a­ture of met­als, help­ing them tran­si­tion to a liq­uid state. Fluorspar has found wide appli­ca­tion not only in met­al­lur­gy but also in the chem­i­cal indus­try, optics, and elec­tron­ics.

Flu­o­rite 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 flux, chem­i­cal, opti­cal, and piezo-opti­cal raw mate­r­i­al.

Characteristics

The main indus­tri­al min­er­al of flu­o­rine is flu­o­rite (CaF₂), but flu­o­rine is also present in cry­o­lite (Na₃[AlF₆]), flu­o­ra­p­atite (Ca₅(PO₄)₃F), bast­nae­site (Ce,Le)[CO₃]F), vil­li­au­mite (NaF). Addi­tion­al­ly, flu­o­rine is found in phl­o­go­pite, topaz, tour­ma­line, and vol­canic glass.

The fol­low­ing vari­eties are dis­tin­guished:

• reg­u­lar flu­o­rite;
• yttri­um flu­o­rite, yttro­flu­o­rite (con­tains up to 14% YF₃);
• opti­cal flu­o­rite (col­or­less and trans­par­ent);
• radi­um flu­o­rite (radioac­tive);
• ceri­um flu­o­rite, cero­flu­o­rite (con­tains up to 15% Y₂O₃ and Ce₂O₃);
• ratovkite (dense, cryp­tocrys­talline or earthy vari­ety of sed­i­men­ta­ry ori­gin);
• chloro­phane (flu­o­resces green when heat­ed).

Flu­o­rite’s col­or can be quite diverse. Usu­al­ly, it comes in vio­let, green, blue, pink-yel­low col­ors of var­i­ous shades and inten­si­ties. The min­er­al’s crys­tal sys­tem is cubic, crys­tal forms are cubes or octa­he­dra. Pen­e­tra­tion twins are char­ac­ter­is­tic. Often forms dense or gran­u­lar mass­es, radi­al-fibrous aggre­gates.

The main phys­i­cal prop­er­ties of flu­o­rite include:

• melt­ing tem­per­a­ture above 1360°C;
• hard­ness (Mohs scale) — 4;
• den­si­ty — 3.18 g/cm³;
• col­ors flame red;
• prac­ti­cal­ly insol­u­ble in water, when dis­solved in hydrochlo­ric acid com­plete­ly decom­pos­es releas­ing hydro­flu­o­ric acid (HF) and hydro­gen sul­fide;
• begins to glow when exposed to ultra­vi­o­let rays;
• changes col­or den­si­ty when heat­ed and glows in the dark;
• quite brit­tle, shat­ters into pieces when struck.

In nature, it occurs in asso­ci­a­tions with quartz, chal­cedony, adu­lar­ia, cal­cite, barite, stib­nite, and cinnabar. As an acces­so­ry min­er­al, it occurs in gran­ites, gran­ite peg­matites, syen­ites, around fumaroles, in car­bon­atites, and alka­line intru­sions.

There are pure flu­o­rite ores (CaF₂ con­tent more than 30%) and com­plex ores (CaF₂ con­tent less than 30%).

By min­er­al com­po­si­tion, pure flu­o­rite ores are divid­ed into:

• quartz-flu­o­rite;
• car­bon­ate-flu­o­rite;
• sil­i­cate-flu­o­rite (mica and feldspar-flu­o­rite);
• barite-flu­o­rite;
• topaz-flu­o­rite.

By min­er­al com­po­si­tion, com­plex ores are divid­ed into:

• flu­o­rite-beryl­li­um;
• flu­o­rite-tin;
• mer­cury-anti­mo­ny-flu­o­rite;
• flu­o­rite-iron ore;
• flu­o­rite-tin-tung­sten.

Fluorite Ore Deposits

Most com­mer­cial flu­o­rite ores are part of hydrother­mal, greisen and car­bon­atite deposits. There are also known deposits in peg­matites, hydrother­mal-sed­i­men­ta­ry and resid­ual deposits. All deposits, except for resid­ual ones, are endoge­nous. Ores are clas­si­fied accord­ing to their CaF₂ con­tent: rich ores with more than 50%, medi­um ores with 35–50%, and ordi­nary ores with up to 35%. Accord­ing to the size of reserves, flu­o­rite deposits are divid­ed into: small — 0.5–2 mil­lion tonnes, medi­um — 2–5 mil­lion tonnes, large — 5–10 mil­lion tonnes, and extra-large — more than 10 mil­lion tonnes.

Hydrother­mal flu­o­rite deposits are asso­ci­at­ed with con­ti­nen­tal vol­canic belts and rifts. High-tem­per­a­ture hydrother­mal deposits (greisen and greisen-scarn rare earth flu­o­rite for­ma­tions) are locat­ed in the areas of con­tact between gran­ites and host rocks. The deposits that occur in the pres­ence of car­bon­ate stra­ta are of prac­ti­cal inter­est. Gran­ites turn into greisens and lime­stones into skarns. Such deposits are char­ac­terised by the asso­ci­a­tion of flu­o­rite with light mica, tour­ma­line, cas­si­terite, topaz, cry­o­lite and oth­er high-tem­per­a­ture min­er­als, with quartz and cal­cite being very rare. Flu­o­rite min­er­al­i­sa­tion is con­cen­trat­ed in skarns, for exam­ple, the Post Riv­er deposit in Alas­ka, and flu­o­rite ores of the Sushchano-Perzhan­sky zone on the Ukrain­ian Shield. Deposits of cry­o­lite feldspar apogran­ites have poten­tial val­ue as a source of flu­o­rine. Such deposits are known in Nige­ria and Green­land.

Medi­um-tem­per­a­ture hydrother­mal deposits (flu­o­rite-barite-poly­metal­lic, flu­o­rite-bertran­dite, flu­o­rite-rare earth for­ma­tions) are locat­ed near the par­ent gran­ite mas­sifs, usu­al­ly in sed­i­men­ta­ry rocks. They are rep­re­sent­ed by both veins and meta­so­mat­ic bod­ies of var­i­ous sizes. The min­er­al com­po­si­tion of the ores is polymin­er­al, includ­ing flu­o­rite, quartz, barite, cal­cite, gale­na, spha­lerite, chal­copy­rite, etc. In deposits that occur in car­bon­ate rocks, hydrother­mal meta­so­ma­tism is man­i­fest­ed. For exam­ple, the Abago­tuyskoye (Trans-Baikal), Aurakhmatskoye (Kaza­khstan), and Pokro­vo-Kyryivske (Donet­sk Oblast) deposits.

Low-tem­per­a­ture hydrother­mal deposits (poly­metal­lic-barite-flu­o­rite and anti­mo­ny-mer­cury-flu­o­rite for­ma­tions) are usu­al­ly found among the main ones, often in car­bon­ate rocks with no or weak man­i­fes­ta­tions of mag­ma­tism (telether­mal, amag­mat­ic deposits). Ore bod­ies occur in car­bon­ate rocks, some­times in sand­stones with car­bon­ate cement. There are known reser­voir meta­so­mat­ic bod­ies and vein for­ma­tions. The main min­er­als are flu­o­rite, cal­cite, gale­na, spha­lerite, chal­copy­rite, mar­c­a­site, barite, kino­var, anti­monite, and bitu­men. The most famous deposits include the Khaidark­an (Kyr­gyzs­tan) and Bakhtyn (Vin­nyt­sia region) fields.

Car­bon­atite deposits (flu­o­rite-rare earth car­bon­atite for­ma­tion) are locat­ed on shields, plat­forms and in areas of com­plete fold­ing. They are com­posed of com­plex flu­o­rite-rare earth ores, in which the main com­po­nents are flu­o­ro­car­bon­ates of rare earths (synchysite, bast­ne­site, parisite), and flu­o­rite is an asso­ci­at­ed min­er­al. The ore bod­ies are rep­re­sent­ed by seam, pipe and lens-shaped bod­ies. Such deposits are com­plex and are sources of not only flu­o­rite, but also rare earths, iron, poly­met­als and barite.

Peg­matite deposits (for­ma­tion of flu­o­rite-bear­ing cham­ber peg­matites) are rather lim­it­ed in dis­tri­b­u­tion. The deposits are rep­re­sent­ed by iso­met­ric and pipe-shaped bod­ies. The peg­matite bod­ies in the cav­i­ties are filled with crys­tals of opti­cal flu­o­rite, mori­on, rauch­topaz, and rock crys­tal. The host rocks are gran­ites (deposits in Kaza­khstan).

In addi­tion to the above-men­tioned types of deposits, flu­o­rite is found in vol­canogenic sed­i­men­ta­ry deposits (Pian­ci­no deposit in Italy), infil­tra­tion deposits (deposits in Sar­dinia), resid­ual debris deposits (Cen­tral Mas­sif in France, deposits in Ken­tucky and Illi­nois), and weath­er­ing crustal deposits.

Deposits in Ukraine

In Ukraine, flu­o­rite deposits are known in the area of the junc­tion of the UC with the DSS (Pokro­vo-Kyryivske deposit, Dokuchaevske, Karakub­ske, Novotroitske occur­rences (Donet­sk oblast)), in Podil­lia (Bakhtynske deposit, Novoselkivske, Skazynetske, Posukhivske, Pereko­rynske, Israil­skyi, Mohyliv-Podil­skyi, Milkivskyi man­i­fes­ta­tions (Vin­nyt­sia oblast)), in the Sushchano-Perzhan­s­ka zone (Cen­tral man­i­fes­ta­tion) (Zhy­to­myr oblast), in the Kirovohrad­s­ka zone (Bobrynets, Kom­pani­ivskyi, Per­voz­vanivskyi man­i­fes­ta­tions (Kirovohrad oblast)) and in the Azov region (Con­stan­tinopol­skyi man­i­fes­ta­tion).

The Pokro­vo-Kyryivske deposit is locat­ed in the junc­tion of the Don­bas and Azov megablocks in the Vol­no­vakha zone and con­sists of three ore bod­ies: Main, North and South. The Main body is lentic­u­lar in shape, 240 m long, 70–180 m wide and 4.4–70 m thick. There are two types of ores: indige­nous ores asso­ci­at­ed with lime­stone of the Tur­neyan stage and delu­vial-pro­lu­vial dis­in­te­grat­ed ores. The ores are rich car­bon­ate-flu­o­rite ores that do not require ben­e­fi­ci­a­tion (CaF₂ — 73–83%), ordi­nary car­bon­ate-flu­o­rite ores (CaF₂ — 38–71%) and car­bon­ate-feldspar-flu­o­rite ores (CaF₂ — 54.3%). The deposit is of medi­um-tem­per­a­ture hydrother­mal-meta­so­mat­ic type. C₁ reserves amount to 1,927 tonnes of ore, C₂ — 300 thou­sand tonnes of ore. It is not cur­rent­ly being devel­oped.

The Bakhtynske deposit is locat­ed with­in the Bakhtyn depres­sion. The flu­o­rite deposit is asso­ci­at­ed with a sand­stone lay­er and is rep­re­sent­ed by sub­hor­i­zon­tal sick­le-shaped and iso­met­ric deposits 4–9.4 km long, 1–3.5 km wide, and rang­ing in depth from 21.3 to 118.5 m. The deposits con­sist of 20 ore bod­ies with an aver­age thick­ness of 0.75–1.45 m, locat­ed one above the oth­er. The ores are of flu­o­rite-car­bon­ate type, with dis­sem­i­nat­ed and vein-type vari­eties. The ores are poor, com­plex, free of harm­ful impu­ri­ties, with flu­o­rite con­tent of 11–41% (17.1–20.6% on aver­age). Ore reserves in the C₁ cat­e­go­ry amount to 4257.5 thou­sand tonnes (CaF₂ — 589.7), C₂ — 13710.3 (CaF₂ — 1920.8), and P₁ resources — 10.8 mil­lion tonnes.

The cen­tral occur­rence is localised among the meta­so­matites of the Sushchano-Perzhan­sky zone. The host rocks are biotite-feldspar and feldspar meta­so­matites, micro­clin­ites, which host flu­o­rine-zir­con-rare earth acces­so­ry min­er­al­i­sa­tion. The main min­er­als are flu­o­rite, zir­con, zir­conite, bast­ne­site, parizite, mon­azite, and xeno­time. Flu­o­rite min­er­al­i­sa­tion was formed dur­ing the greiseni­sa­tion of the Perzhan­sky gran­ites. The ore bod­ies are of a bed­ded and lentic­u­lar shape, rang­ing in thick­ness from the first few cm to 25 m. The flu­o­rite con­tent varies from the first per cent to 53.8%, with an aver­age grade of 28%. Flu­o­rite ores con­tain con­cen­tra­tions of rare earth ele­ments, main­ly yttri­um.

Areas of use

The main con­sumer of flu­o­rite is the chem­i­cal indus­try. Ele­men­tal flu­o­rine is used in organ­ic syn­the­sis and nuclear physics. It is used to pro­duce nuclear fuel and to split ura­ni­um into the iso­topes ²³⁸U and ²³⁵U. Flu­o­rine com­pounds with oxy­gen or halo­gens are strong oxi­dants and are used to burn rock­et and jet fuel. The fol­low­ing qual­i­ty require­ments apply to flu­o­rite used in the chem­i­cal indus­try: CaF₂ con­tent of at least 95% and no more than 1% SiO₂ and CaO, and no impu­ri­ties of bar­i­um, lead or sul­phur.

In fer­rous met­al­lur­gy, fluorspar is used as a flux in open-hearth steel­mak­ing, as well as for some fer­roal­loys in elec­tric fur­naces and foundries. In fer­rous met­al­lur­gy, fluorspar is used with a CaF₂ con­tent of 75 to 92% (depend­ing on the qual­i­ty of steel and fer­roal­loys) and no more than 0.2–1.5% sul­phur. Flu­o­rite should be in pieces larg­er than 3 mm (10–15 mm).

In small quan­ti­ties, flu­o­rite is used to make cement, opaque frost­ed glass and enam­el. Flu­o­rite grade F‑85 is used for glass and enam­el pro­duc­tion. The con­tent of iron oxide is 0.06–0.12%, CaCO₃ is no more than 2.5%. Ores with a CaF₂ con­tent of 55–45% are used in the cement indus­try.

Pure, trans­par­ent flu­o­rite crys­tals are used as opti­cal raw mate­ri­als (for the man­u­fac­ture of lens­es for micro­scope lens­es, prisms for stec­tro­graphs, and plates for short-wave devices). Opti­cal flu­o­rite is sub­ject to the high­est indus­tri­al require­ments. The size of the crys­tals or their frag­ments must be at least 10 mm across and they must be free of cracks and inclu­sions of oth­er min­er­als. Since opti­cal flu­o­rite is rarely found in nature, syn­thet­ic crys­tals have recent­ly been used for these pur­pos­es.

Flu­o­ri­nat­ed poly­mers, such as Teflon, are used in engi­neer­ing and med­i­cine due to their resis­tance to acids and alka­lis. Flu­o­ro­plas­tics are used to make pumps, and flu­o­ri­nat­ed rub­bers are known for their heat resis­tance. Flu­o­rine-con­tain­ing lubri­cants, anti-can­cer drugs and alco­hol treat­ment are also pro­duced using flu­o­rine. Flu­o­ri­da­tion of water and tooth­pastes helps pre­vent tooth decay. Rock­et fuel, chem­i­cal lasers, and refrig­er­a­tors use fre­ons and oth­er flu­o­ri­nat­ed com­pounds. Hydro­gen flu­o­ride is used as a cat­a­lyst in chem­i­cal reac­tions, and sodi­um flu­o­ride is used to treat wood and make acid-resis­tant mate­ri­als.

Fluorspar (flu­o­rite) is an impor­tant min­er­al wide­ly used in met­al­lur­gy, chem­i­cals, optics and elec­tron­ics due to its unique prop­er­ties, such as the abil­i­ty to low­er the melt­ing point of met­als and glow under ultra­vi­o­let light. It has var­i­ous indus­tri­al vari­eties and deposits, which can be com­plex and con­tain rare ele­ments. Ukraine has sig­nif­i­cant reserves of flu­o­rite, which makes this min­er­al strate­gi­cal­ly impor­tant for the coun­try’s econ­o­my. Effec­tive devel­op­ment of flu­o­rite deposits requires a ratio­nal approach and inno­v­a­tive min­ing meth­ods.