Saponite. Char­ac­ter­is­tics, dis­tri­b­u­tion, appli­ca­tion

Saponite is an amor­phous min­er­al sim­i­lar to mont­mo­ril­lonite. Its struc­ture is rep­re­sent­ed by scaly, earthy, clay-like dense mass­es, as well as fibrous aggre­gates, spherulites and occa­sion­al­ly small sta­lac­tites. When wet, it is soft and greasy to the touch, and when dry, it forms a dense porous mass. The min­er­al is char­ac­terised by per­fect cleav­age along the (001) plane.

Saponite 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 a raw mate­r­i­al for agro­chem­i­cals and min­er­al pig­ments.

Physical and chemical properties

Saponites (mag­ne­sium smec­tites) are a group of tri­oc­ta­he­dral fine­ly dis­persed lay­ered sil­i­cates and alu­mi­nosil­i­cates of the 2:1 struc­tur­al type. They belong to the mont­mo­ril­lonite group, where Al³⁺ is almost com­plete­ly replaced by mag­ne­sium in the octa­he­dral lat­tice of the min­er­al, and Si⁴⁺ in the tetra­he­dral lat­tice is par­tial­ly replaced by Al³⁺. Saponites are char­ac­terised by a swelling struc­ture and high sorp­tion prop­er­ties.

Chem­i­cal for­mu­la Mg3[(OH)2|Al0.33Si3.67O10]•nH2O.
Approx­i­mate com­po­si­tion of saponite: SiO₂ — 39.6–54.7%, Al₂O₃ — 3.9–10.2%, MgO — 15.8–33.3%, Fe₂O₃ — 0.2–12.0%, FeO — 0–7.8%, CaO — 0–2.9% , Na2O — 0–0.7%, K2O — 0–0.3%, TiO2 — 0–0.4%, MnO — 0–0.3 H2O + (struc­tur­al water OH) — 4.2–12.0, H2O-(hydration water) — 7.2–17.4.

The colour of saponite clays varies from yel­low­ish to brown or grey­ish-green, and the frac­ture is uneven.
Lab­o­ra­to­ry stud­ies have revealed the fol­low­ing phys­i­cal prop­er­ties:

• actu­al spe­cif­ic grav­i­ty: 2.65–2.97 g/cm3,
• aver­age den­si­ty — 1876–2160 kg/m3,
• plas­tic­i­ty — 28.4
• hard­ness on the Mohs scale — 1.5–2.5,
• poros­i­ty — 23.13–36.82%,
• water absorp­tion — 11.79–25.01%,
• mois­ture con­tent — 23.33%,
• refrac­tori­ness — 1280–1300°C,
• loose­ness coef­fi­cient — 1.67.

Saponite and saponite-bear­ing rocks con­sist main­ly of lay­ered alu­mi­nosil­i­cates. The main rock-form­ing min­er­al is tri­oc­ta­he­dral smec­tite-saponite. Small amounts of dioc­ta­he­dral smec­tite (up to 7–10%), anal­cime (up to 35% in the low­er hori­zon, 3–8% in the upper hori­zon), as well as cal­cite, hematite, quartz, anatase and chlo­rite.

Distribution of saponite

Indus­tri­al deposits of saponite raw mate­ri­als were first dis­cov­ered in Ukraine in the 1970s on the west­ern slope of the Ukrain­ian Shield, where saponite clays form the ben­tonite province. Here, they are con­fined to the weath­ered crust of basalt tuffs of the Volyn series of the Ven­di­an peri­od.

In the Khmel­nyt­skyi region, four deposits of saponite clays have been explored: Tashkivske‑I, Tashkivske-II, Radoshiv­ske and Var­varivske, with total reserves esti­mat­ed at 10–20 mil­lion tonnes. Saponite is already being mined at one of the deposits in a small quar­ry, and the prod­uct is processed in the city of Slavu­ta.

The saponite and saponite-bear­ing rocks of the Var­varivske deposit are main­ly rep­re­sent­ed by a high­ly dis­persed clay min­er­al. In the upper hori­zon (depth 20–40.9 m), the saponite rock is brown or dark brown in colour, loose when dry, some­times fri­able, with thin, com­pact­ed, hor­i­zon­tal­ly lay­ered inter­lay­ers of green­ish and light grey tones. In the low­er hori­zon (depth 40–70 m), the rocks are dense, mono­lith­ic, dark brown in colour and have a con­choidal frac­ture.

The qual­i­ty assess­ment of saponite from the Var­varivskyi deposit is based on the require­ments of indus­try tech­ni­cal con­di­tions approved by the head of the State Depart­ment of Vet­eri­nary Med­i­cine of the Min­istry of Agrar­i­an Pol­i­cy of Ukraine, reg­is­tered at the Khmel­nyt­skyi State Cen­tre for Stan­dards, Metrol­o­gy and Cer­ti­fi­ca­tion under No. 102/000952 — TU U 24.4–13973968-003‑2003 ‘Saponite flour ’Sapoko­rm”. Accord­ing to the tech­ni­cal spec­i­fi­ca­tions, saponite flour is used in ani­mal hus­bandry and poul­try farm­ing as a nat­ur­al min­er­al pro­phy­lac­tic and ther­a­peu­tic feed addi­tive, a growth and health stim­u­lant for ani­mals and poul­try, and as a sor­bent.

Accord­ing to the litho­log­i­cal sec­tion, the Var­varivske deposit is rep­re­sent­ed by the fol­low­ing lay­ers:

• Cov­er lay­er — lime­stones, lime­stone sand­stones (up to 0.6 m);
• Ben­tonite rocks (4.5–6 m);
• Siliceous rocks (up to 1–1.5 m);
• Saponite lay­er (up to 70–80 m).

By anal­o­gy with the Var­varivskyi deposit, the min­er­al resource of the Tashkivska‑1 site is rep­re­sent­ed by a strat­i­form deposit of argilla­ceous saponite clays of the Babyn­s­ka For­ma­tion of the Ven­di­an, con­fined to the weath­er­ing crust of basalt tuffs of the Berestovets Hori­zon of the Volyn Series of the Low­er Cam­bri­an, dense, with well-pre­served struc­tur­al fea­tures of tuffa­ceous rock frag­ments, brown, red­dish-brown, green­ish and grey in colour, thin-lay­ered tex­ture, with a thick­ness of 17.0 to 40.3 m. The over­bur­den rocks include chalk deposits rep­re­sent­ed by flint nod­ules cement­ed with sandy-clayey mate­r­i­al, chal­cedono­lites, Qua­ter­nary sands and a soil-plant lay­er with a total aver­age thick­ness of 18.4 m.

Uses of saponite

Saponite, enriched with chem­i­cal ele­ments such as alu­mini­um, cal­ci­um, iron, hydro­gen, mag­ne­sium, oxy­gen, tita­ni­um, man­ganese, sodi­um, potas­si­um and phos­pho­rus, has a wide range of appli­ca­tions in agri­cul­ture and indus­try. Due to its prop­er­ties, it is used for min­er­al feed­ing of ani­mals, as a preser­v­a­tive for green fod­der, and as a feed improver. Saponite is also effec­tive for the recla­ma­tion of land con­t­a­m­i­nat­ed with radionu­clides.

The mag­ne­sium vari­ety of saponite clays, also known as ben­tonite clays, is wide­ly used in more than 80 indus­tries in devel­oped coun­tries. They are an impor­tant com­po­nent of inter­na­tion­al export and import oper­a­tions, which indi­cates their high eco­nom­ic val­ue. Ukraine, for exam­ple, needs more than 4 mil­lion tonnes of saponite raw mate­ri­als annu­al­ly, of which 3 mil­lion tonnes are required for live­stock farm­ing alone.

Saponite clays can serve as nat­ur­al fer­tilis­ers that help increase yields of corn, wheat, rye and oth­er grain crops. In par­tic­u­lar, the high mag­ne­sium con­tent in saponite and its neu­tral­is­ing prop­er­ties can sig­nif­i­cant­ly increase the yield of sod-pod­zolic soils, which occu­py a sig­nif­i­cant part of the arable land in the Ukrain­ian Polis­sya region.

Saponite and glau­conite can be used in feed­ing broil­er chick­ens as addi­tives or com­po­nents of com­pound feed in an amount of 4–6% of the total feed mass. The use of these nat­ur­al min­er­als has a pos­i­tive effect on the diges­tive sys­tem of poul­try, in par­tic­u­lar, it con­tributes to an increase in feed nitro­gen absorp­tion by 1.0–1.3% and improves fibre digestibil­i­ty. Due to their prop­er­ties, saponite and glau­conite slow down the pas­sage of feed through the gas­troin­testi­nal tract, which reduces the mois­ture con­tent of the feed in the intes­tine by 1.2–3.8%.

In addi­tion, these min­er­als have a pos­i­tive effect on the phys­i­o­log­i­cal state of broil­ers. They con­tribute to an increase in vit­a­min A con­tent in the liv­er by 33.4 μg, increase the lev­el of fat­ty acids in the diet by 0.12–4.06% and increase the con­cen­tra­tion of haemo­glo­bin in the blood. As not­ed by M.F. Kulik, the intro­duc­tion of saponite and glau­conite into the feed of farm poul­try con­tributes to an increase in the sur­vival rate of broil­er chick­ens by 1.0–2.0%, their live weight by 0.9–7.4%, and also reduces feed costs per unit of growth by 1.2–7.4%.

Based on saponite raw mate­ri­als, Ukrain­ian sci­en­tists have cre­at­ed a feed addi­tive called ‘Fis­tash­ki’, which is pro­duced by the exper­i­men­tal plant of the Vin­nyt­sia Sci­en­tif­ic and Pro­duc­tion Asso­ci­a­tion ‘Min­dozy­vi­va’. This prod­uct is wide­ly used in ani­mal hus­bandry to improve the diet of ani­mals and birds.

In phar­ma­col­o­gy, saponite is used as an adsor­bent, vis­cos­i­ty-enhanc­ing agent, sus­pend­ing agent or emul­si­fi­er, and is use­ful as a struc­tur­al com­po­nent in semi-sol­id cos­met­ic and med­ical prod­ucts. It is also used in the devel­op­ment of gas­troin­testi­nal X‑ray con­trast agents and prepa­ra­tions intend­ed for pro­longed deliv­ery to the gas­troin­testi­nal tract.