Vermiculite (from Latin vermiculus - a worm) is a mineral from the group of hydromica with a layered structure. The product of the secondary change ( hydrolysis and subsequent weathering ) of dark mica biotite and phlogopite .
| Vermiculite | |
|---|---|
 | |
| Formula | (Mg +2 , Fe +2 , Fe +3 ) 3 [(AlSi) 4 O 10 ] ⋅ (OH) 2 ⋅4H 2 O |
| Physical properties | |
| Colour | brown, yellowish brown, golden yellow, bronze yellow, greenish to blackish. |
| Trait color | white, yellowish, shiny |
| Shine | oily, glass (pearly on cleavage planes) |
| Hardness | 1-1.5 |
| Cleavage | good basis (001) |
| Kink | the mineral is split into thin leaves |
| Density | 2.4-2.7 (expanded - 0.065-0.130) g / cm³ |
| Syngonia | |
Represents large plate crystals of golden yellow or brown color. When heated, worm-shaped columns or threads of golden or silver color are formed from the plates with a transverse division into the thinnest scales (expanded vermiculite). Calcined masses of vermiculite float freely on the surface of the water.
The chemical composition corresponds to the approximate formula (Mg +2 , Fe +2 , Fe +3 ) 3 [(Al, Si) 4 O 10 ] · (OH) 2 · 4H 2 O. However, vermiculite rarely corresponds to the general formula and usually contains impurities.
Content
Synonyms
- Brodrickite
- Kalsajiite (culsageeite)
- Jefferisite
- Zonolite [1]
Varieties
- Batavite is a non-iron type of vermiculite found in Germany (Kropfmuhl Mine, Bavarian Forest, Lower Bavaria).
- Copper vermiculite (copper vermiculite) - a copper-containing variety of vermiculite.
- Eastonite (eastonite) - silver-white vermiculite.
- Lucasite (lucasite) - chromic vermiculite.
- Vaalite is a type of vermiculite with the stoichiometric formula (Mg, Fe) 7 (Si, Al, Fe) 8 O 20 (OH) 4 ⋅ 2H 2 O found in South Africa [1] .
Properties
- hardness on a mineralogical scale of 1-1.5;
- a density of 2.4-2.7 g / cm 3 (expanded - 0.065-0.130 g / cm 3 );
- melting point 1350 ° C;
- resistant to abrasion and similar to graphite in lubricating properties;
- when heated to a temperature of 900–1000 ° C, it swells and increases in volume by 15–25 times.
Vermiculite is biologically resistant - it is not subject to decomposition and rotting under the influence of microorganisms , it is not a favorable environment for insects and rodents , and it is also chemically inert - it is neutral to the action of alkalis and acids .
Deposits
Vermiculite was first discovered at the beginning of the 19th century; it got industrial use only after 100 years. For the development of several technologies for its application, Yakub Akhtyamov received in 1979 a prize of the USSR Council of Ministers for "Research, development of technology and the introduction of vermiculite and products based on it" in the national economy.
The world's largest Kovdorskoye field on the Kola Peninsula ( Murmansk Region ). Vermiculite is found in the Urals near the city of Vishnevogorsk ( Chelyabinsk Region ), in the Krasnoyarsk Territory - the Tatarskoye Field, the Irkutsk Region - the upper reaches of the Uluntuy Paddy and the city of Slyudyanka, Primorsky Krai - the Koksharovskoye Field. Abroad - in Western Australia , USA (Montana, Colorado, Wyoming, North Carolina, Georgia), Uganda , Ukraine , South Africa , Kazakhstan (Kulantau deposit in South Kazakhstan ), Uzbekistan ( Karakalpakia ).
Application
In economic activity, exclusively expanded vermiculite is used.
Crop and livestock
Vermiculite is most popular in crop production , where it is used as a substrate for mulching and aeration of the soil, saturates plants with useful minerals.
Widely used in crop production and in hydroponics .
Vermiculite has a high coefficient of water absorption - 400-530% (100 g of vermiculite absorb 400-530 ml of water). It easily absorbs moisture and also gives it away easily, creating an optimally moist environment for feeding plant roots. In agriculture, vermiculite is used to improve soil structure; it is even called an “agronomic” rock.
In European countries, vermiculite is used for pets (cat toilets, ground for snakes, spiders). It is also used to incubate reptile eggs.
Industrial products
Vermiculite is used for the manufacture of heat-insulating products, sound-absorbing materials, including those in the aviation and automotive industries , lightweight concrete , and decorative plaster mortars. In addition, it is used as a filler in the manufacture of wallpaper , rubbers , plastics , paints , pesticides , and in the production of antifriction materials . Adsorbent for gaseous and liquid industrial wastes. In nuclear energy it is used as a reflector of gamma radiation and an absorber of radiation of radioactive isotopes of chemical elements , for example, strontium-90 , cesium-137 , cobalt-58 .
Insulation materials
The elasticity of the structure of vermiculite gives it significant advantages over similar materials. So, perlite used for thermal insulation is extremely fragile and is destroyed even during transportation. Vermiculite is devoid of this drawback, which makes it possible to produce heat and fireproof materials from it by pressing. Vermiculite is used as part of fire-retardant coatings, as well as a heat-insulating filler of fire-resistant doors, a filler of heat and sound insulating building mixtures.
- application temperature - from −260 ° C to +1200 ° C;
- pH 6.8-7.0 (slightly acidic - neutral);
- magnesium content - 10-14%, potassium - 3-5%, calcium - 1.2-2%, manganese - 0.8-1%, iron - 5.6-6.5%, silicon - 34−36% .
Asbestos pollution
Vermiculite can be contaminated with asbestos , since the geological processes of formation of both minerals are similar. Currently, vermiculite mines around the world are regularly checked and it is assumed that their products should not contain asbestos.
Pure vermiculite does not contain asbestos and is not toxic.
Notes
Links
- Report by A. I. Nizhegorodov at the 2010 conference on a new method of Expansion of Vermiculite (inaccessible link)
- GOST 12865-67 " Expanded Vermiculite"
- Setinskaya O. A. Issues of using vermiculite in indoor floriculture . donnaflora.ru. Date of treatment July 23, 2014.
- Vermiculite / 10/01/2012 Kalacheva-Lezhneva N. G. "Kyshtym 74.ru"