ASKAN BENTONITE FIELD

Industrial mining of bentonite in Georgia dates back to 1946, when Academician Al. Tvalchrelidze was founded the first quarry of the extraction of bentonite clay in the village Mtispiri of Ozurgeti district. From the very beginning of the extraction of bentonite, Academician Tvalchrelidze was aware of the need for scientific support of the mining industry, and for this purpose he organized the Caucasian Institute of Mineral Raw Materials (CIMS) in Tbilisi. Due to this, the geology, genesis, material composition and technological properties of the bentonite clays of the Askansk deposit were studied in sufficient detail. These scientific developments made it possible to create a new branch of industry in the 40s-50s of the last century in the USSR in the 40s-50s – the production of bentonite clay products for various industries and agriculture.
In the period from the 50s to the 90s of the last century, the Makharadze mine department of bentonite and the production of a wide range of products for use in various industries worked on the basis of the Askansk deposit. Volumes of bentonite mining and processing reached 200 thousand by the end of the 80s. t./year. The main deliveries of bentonite were carried out at automobile plants of the USSR, including AvtoVAZ (Togliatti, Russia), Yaroslavl Motor Plant, KamAZ, GAZ, machine-building enterprises of the Belarusian and Ukrainian SSR, as well as wine refineries, oil and gas well drilling enterprises, oil refineries.
Currently, AAG is licensed to use subsoil for the extraction of bentonite in two areas of the Askan deposit – Tsikhis-Ubani and Vanis-Kedi. At both sites, quarries are currently equipped and bentonite clay is being mined.
The high-quality bentonite Askansk deposit has been known since the beginning of the 20th century thanks to the expedition organized by academician Fersman in 1913. The deposit was named after one of the first finds of bentonite clay near the village of Askana in the Ozurget district of the Guri region.
Bentonite clay deposits are located in a mountainous area at an altitude of about 400 meters above sea level, where the spurs of the South Caucasus Range descend into the Colchis Valley near the town of Ozurgeti (Makharadze during Soviet times). The field consists of a number of separate areas: Tsikhis-Ubani, Vanis-Kedi, Mtis-Piri, Uchubi and others, which are several kilometers apart from each other. The reserves of each of the sites range from 4.5 million tons. up to 9 million tons and more. All these bentonite deposits are associated with a common geological history of formation and form a group of deposits of alkaline and alkaline-earth bentonites of volcanic genesis. Parent rocks of the Askan bentonite served as a thick stratum of pumiceous andesite-trachyte tuffs of the Middle Eocene, which underwent secondary changes. As a result of these changes, deposits of high quality bentonite clays were formed, with a small amount of impurities of other minerals. The main properties of bentonite clays of the Askan deposit are given in Tables 1 and 2.

The chemical composition of the bentonites of the Askan field
(data from the report on geological exploration of the Askan field)
№
 BREED
Chemical components
SiO2
Al2O3
Fe2O3
FeO
TiO2
MnO
CaO
MgO
Na2O
K2O
SO3
1
 Quarry Tsikhis-Ubani
1.1.
 Askangel
54,20
17,12
3,95
1,00
0,33
0,06
1,50
3,98
2,80
2.0
0,17
1.2.
 Askanglina
51,40
16,86
3,29
1,00
0,25
0,04
2,0
4,71
0,65
0,5
0,16
1.3.
 Askangel1
59,50
18,60
3,50
н/д
0,40
н/д
2,30
4,50
2,40
1,30
0,18
2
 Quarry Vanis Kedi
2.1.
 Askanglina
53,14
18,0
4,61
1,08
0,40
0,25
4,55
4,65
1,15
2,8
0,96
1D. Koch European Bentonites as alternatives to MX-80 //Science and Technology Series N 334 (2008), p.29-30
Composition and properties of bentonite at the Askan deposit
(in comparison with bentonite from Milos island (Greece) and Wyoming bentonite MX-80, USA1)
№ 
 Indicators
Bentonites
Askan,
Georgia, uch. Tsikhis-Ubani
Са-bentonite,
about. Milos, Greece
Na-bentonite
MX – 80, Wyoming, USA
1
 Mineral composition (XRD – X-ray diffraction analysis)
1.1.
Smectite, (%)
85-95
75-85
65-75
1.2.
Illit, (%)
2-6
< 4
2-4
1.3.
Quartz, (%)
< 4
< 4
5-7
1.4.
Calcite, (%)
3-5
8 – 12
6 – 9
1.5.
Other, (%)
< 4
< 4
5-16
2
 Physical properties
2.1.
 Cation exchange capacity, mg.equiv./100gr.
95 – 105
80 – 90
70 – 80
2.2.
 Swelling Index, ml. / 2g.
22 – 26
6 – 10
28 – 32
2.3.
Water adsorption (Enslin-Neff), %
480 – 520
110 – 150
650 – 800
1D. Koch European Bentonites as alternatives to MX-80 //Science and Technology Series N 334 (2008), p.29-30
Characteristic features of bentonite at the Askan deposit are:
  1. The presence of alkaline and alkaline-earth varieties of bentonite, named respectively Ascangel and Ascangline;
  2. High capacity of cationic exchange of montmorillonite – 95 – 105 mg.eq./100gr .;
  3. High content of montmorillonite – mostly 85 – 95%;
  4. The low iron content in montmorillonite is predominantly 2.7 – 3.5%.
Low iron montmorillonite predetermines the high thermal stability of Ascanian bentonite in the foundry industry – which is especially important in the case of cast iron production, when a large amount of anti-carbon carbon additives are introduced into the molding mixture, greatly reducing the binding capacity of high-iron bentonites.