Vermiculite
Encyclopedia
Vermiculite is a natural mineral
that expands with the application of heat
. The expansion process is called exfoliation
and it is routinely accomplished in purpose-designed commercial furnaces. Vermiculite is formed by weathering
or hydrothermal alteration of biotite
or phlogopite
. Large commercial vermiculite mines currently exist in Russia
, South Africa
, China
, and Brazil
.
, Worcester County, Massachusetts
, USA. Its name is from Latin
vermiculare, to breed worms, for the manner in which it exfoliates
when heated.
It typically occurs as an alteration product at the contact between felsic
and mafic
or ultramafic rocks such as pyroxenite
s and dunite
s. It also occurs in carbonatite
s and metamorphosed
magnesium rich limestone
. Associated mineral phases include: corundum
, apatite
, serpentine and talc
. It occurs interlayered with chlorite
, biotite and phlogopite.
, meaning it has 2 tetrahedral sheets for every one octahedral sheet. It is a limited expansion clay with a medium shrink-swell capacity
. Vermiculite has a high cation exchange capacity
at 100-150 meq/100 g. Vermiculite clays are weathered mica
s in which the potassium
ions between the molecular sheets are replaced by magnesium
and iron
ions.
In 2005, South Africa was the top producer of vermiculite with about 40% world share followed by the USA and China, reports the British Geological Survey
.
While some exfoliators focus on only a few of the possible applications, others can provide vermiculite products for all its applications. It is common for vermiculite exfoliators to exfoliate perlite also, as both are often sold together. For those who want to set up a new exfoliation process, it is possible to find expert consultants to advise in the design and construction of the desired facilities. Vermiculite exfoliators have an international trade association called The Vermiculite Association to represent the industry's interests and to exchange information. Many of its members also maintain memberships in The Perlite Institute.
fibres. The cement
itious versions of these fireproofing sprays contain Portland cement
and lightweight aggregates
of the plaster
vermiculite. Vermiculite ore, particularly those mined from the U.S., usually is contaminated with asbestos. Danger of exposure to asbestos in these sprays is greatly increased when not handling following proper industrial hygiene
procedures.
until the early 1990s. Vermiculite mines throughout the world are now regularly tested for it and are supposed to sell products that contain no asbestos. The former vermiculite mine in Libby
, Montana
, did have tremolite
asbestos as well as winchite and richterite
(both fibrous amphiboles) — in fact, it was formed underground through essentially the same geologic processes as the contaminants. A vermiculite mine in Virginia
has also been found to be contaminated by asbestos.
Pure vermiculite does not contain asbestos and is non-toxic, but it can become contaminated over long periods if there is a presence of a secondary mineral called diopside
. After millions of years of weathering, the biotite
turns into vermiculite and the diopside turns into asbestos.
, and the vermiculite was sold under the commercial name Zonolite. The Zonolite brand and the mine was acquired by the W.R. Grace Company in 1963. Mining operations at the Libby site stopped in 1990 in response to asbestos contamination. While in operation, the Libby mine may have produced 80% of the world's supply of vermiculite.
The United States government estimates that vermiculite was used in more than 35 million homes, but does not recommend its removal. Nevertheless, homes or structures containing vermiculite or vermiculite insulation dating from before the mid 1990s—and especially those known to contain the "Zonolite" brand—may contain asbestos
, and therefore may be a health concern.
An article published in the Salt Lake Tribune on December 3, 2006, reported that vermiculite and Zonolite had been found to contain asbestos
, which had led to cancers such as those found in asbestos-related cases. The article stated that there had been a "cover-up" by W.R. Grace Company
and others regarding the health risks associated with vermiculite and that several sites in the Salt Lake Valley
had been remediated by the EPA
when they were shown to be contaminated with asbestos. W.R. Grace Company has vigorously denied these charges.
The vermiculite deposit at the mine in Libby, Montana, was (and is) heavily contaminated with asbestos. Numerous people were knowingly exposed to the harmful dust of vermiculite that contained asbestos. Unfortunately, the mine had been operating since the 1920s, and environmental and industrial controls were virtually non-existent until the mine was purchased by the W.R. Grace Company in 1963. Yet, knowing the human health risks, the mining company still continued to operate there until 1990. Consequently, many of the former miners and residents of Libby have been affected and continue to suffer health problems. Over 200 people in the town have died from asbestos-related disease due to contamination from vermiculite mining from nearby Zonolite Mountain, where soil samples were found to be loaded with fibrous tremolite
(known to be a very toxic form of asbestos), and countless others there who insulated their homes with Zonolite have succumbed to asbestos-related diseases, most of whom never were employed in environments where asbestos was an issue.
After a 1999 Seattle Post-Intelligencer
story claimed that asbestos-related disease was common in the town, the EPA
, in response to political pressure, made cleanup of the site a priority and called Libby the worst case of community-wide exposure to a toxic substance in U.S. history. The EPA has spent $120 million in Superfund
money on cleanup. In October 2006, W. R. Grace Company tried to appeal the fines levied on them from the EPA, but the Supreme Court rejected the appeal. The United States government is also pursuing criminal charges against several former executives and managers of the mine for allegedly disregarding and covering up health risks to employees. They are also accused of obstructing the government's cleanup efforts and wire fraud. To date, according to the indictment, approximately 1,200 residents of the Libby area have been identified as suffering from some kind of asbestos-related abnormality. Jury selection was to have been completed in February, 2009.
The case ended in acquittals on May 8, 2009. On June 17, 2009, the EPA issued a public health emergency in and near Libby, thereby allowing Federal agencies to provide funding for health care, and for removal of contaminated insulation from affected homes.
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
that expands with the application of heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
. The expansion process is called exfoliation
Exfoliation
Exfoliation has several meanings:* Exfoliation describes the loss of leaves from a plant.* Exfoliation , is a cosmetic technique aimed at removing dead skin cells from the face and body....
and it is routinely accomplished in purpose-designed commercial furnaces. Vermiculite is formed by weathering
Weathering
Weathering is the breaking down of rocks, soils and minerals as well as artificial materials through contact with the Earth's atmosphere, biota and waters...
or hydrothermal alteration of biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
or phlogopite
Phlogopite
Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica.Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg3AlSi3O102. Iron substitutes for magnesium in variable amounts...
. Large commercial vermiculite mines currently exist in Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, and Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
.
Occurrence
Vermiculite was first described in 1824 for an occurrence in MillburyMillbury
Millbury may refer to a location in the United States:* Millbury, Massachusetts* Millbury, Ohio...
, Worcester County, Massachusetts
Worcester County, Massachusetts
-Demographics:In 1990 Worcester County had a population of 709,705.As of the census of 2000, there were 750,963 people, 283,927 households, and 192,502 families residing in the county. The population density was 496 people per square mile . There were 298,159 housing units at an average density...
, USA. Its name is from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
vermiculare, to breed worms, for the manner in which it exfoliates
Exfoliation
Exfoliation has several meanings:* Exfoliation describes the loss of leaves from a plant.* Exfoliation , is a cosmetic technique aimed at removing dead skin cells from the face and body....
when heated.
It typically occurs as an alteration product at the contact between felsic
Felsic
The word "felsic" is a term used in geology to refer to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium....
and mafic
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
or ultramafic rocks such as pyroxenite
Pyroxenite
Pyroxenite is an ultramafic igneous rock consisting essentially of minerals of the pyroxene group, such as augite and diopside, hypersthene, bronzite or enstatite. They are classified into clinopyroxenites, orthopyroxenites, and the websterites which contain both pyroxenes...
s and dunite
Dunite
Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse-grained or phaneritic texture. The mineral assemblage is greater than 90% olivine, with minor amounts of other minerals such as pyroxene, chromite and pyrope. Dunite is the olivine-rich end-member of the peridotite group...
s. It also occurs in carbonatite
Carbonatite
Carbonatites are intrusive or extrusive igneous rocks defined by mineralogic composition consisting of greater than 50 percent carbonate minerals. Carbonatites may be confused with marble, and may require geochemical verification....
s and metamorphosed
Metamorphism
Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
magnesium rich limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
. Associated mineral phases include: corundum
Corundum
Corundum is a crystalline form of aluminium oxide with traces of iron, titanium and chromium. It is a rock-forming mineral. It is one of the naturally clear transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red...
, apatite
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
, serpentine and talc
Talc
Talc is a mineral composed of hydrated magnesium silicate with the chemical formula H2Mg34 or Mg3Si4O102. In loose form, it is the widely-used substance known as talcum powder. It occurs as foliated to fibrous masses, its crystals being so rare as to be almost unknown...
. It occurs interlayered with chlorite
Chlorite group
The chlorites are a group of phyllosilicate minerals. Chlorites can be described by the following four endmembers based on their chemistry via substitution of the following four elements in the silicate lattice; Mg, Fe, Ni, and Mn....
, biotite and phlogopite.
Structure
Vermiculite is a 2:1 clayClay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
, meaning it has 2 tetrahedral sheets for every one octahedral sheet. It is a limited expansion clay with a medium shrink-swell capacity
Shrink-swell capacity
The Shrink-swell capacity of clay refers to the extent to which a clay will expand when wet and retract when dry. Soil that is problematic due to high capacity is known as shrink-swell soil, or expansive soil.-Description:...
. Vermiculite has a high cation exchange capacity
Cation exchange capacity
In soil science, cation-exchange capacity is the maximum quantity of total cations, of any class, that a soil is capable of holding, at a given pH value, for exchanging with the soil solution. CEC is used as a measure of fertility, nutrient retention capacity, and the capacity to protect...
at 100-150 meq/100 g. Vermiculite clays are weathered mica
Mica
The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...
s in which the potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
ions between the molecular sheets are replaced by magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
and iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
ions.
Commercial uses
- moulded shapes bonded with sodium silicateSodium silicateSodium silicate is the common name for a compound sodium metasilicate, Na2SiO3, also known as water glass or liquid glass. It is available in aqueous solution and in solid form and is used in cements, passive fire protection, refractories, textile and lumber processing, and automobiles...
- this process involves the mixing of exfoliated vermiculite with potassium and/or sodium silicate to produce an 'earth damp' mixture. This material is then hydraulically pressed into shape in a mould, and then heat cured at temperatures up to 180° C for up to 24 hours depending upon the thickness of the board. Boards produced in this way can withstand service temperatures of up to 1150° C and are often used in the aluminium smelting industry as back-up insulation behind the carbon cathode in the potcells which contain the molten mixture of cryolite and alumina. These products are used in:- high-temperature insulation
- refractory insulation
- acoustic panels
- fireproofing of structural steelSteelSteel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
and pipePipe (material)A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases , slurries, powders, masses of small solids...
s
- calcium silicate boards - exfoliated vermiculite is added to a calcium silicate slurry, this is then dewatered by pressing or by using one of the Fourdriner/Magnani/Hatschek processes to form a flat board which is then heat cured under pressure (typically 10-15 bar) for periods up to 24 hours.
- brake linings - finer grades of exfoliated vermiculite are being used in brake linings primarily for the automotive market The properties of vermiculite that make it an appropriate choice for use in brake linings include its thermal resistance, ease of addition to other raw materials achieve a homogenous mix and its shape and surface characteristics
- roof and floor screeds and insulating concretes - exfoliated vermiculite (typically the finer grades) can be added at site to portland cement and other aggregates, rheological aids and water to produce roof and floor concrete screeds or lightweight concrete which have the benefit of being lightweight and insulating. In many cases vermiculite based roof screeds are often used in conjunction with other insulation materials such as polystyrene board to form a total roofing system. A bituminous binder can also be used with exfoliated vermiculite can to produce a dry, lightweight roof screed which has the advantages of low thermal conductivity, low moisture content and ease of placement by pouring from the bag and then tamping.
- soilless growing media - exfoliated vermiculite is combined with other materials such as peat or composted pine bark compost to produce soilless growing media for the professional horticulturalist and for the home gardener. These mixes promote faster root growth and gives quick anchorage to young roots. The mixture helps retain air, plant food and moisture, releasing them as the plant requires them. These mixes were pioneered by Boodley and Sheldrake
- seed germination - either used alone or mixed with soil or peat, vermiculite is used to germinate seeds. Very little watering is required. When vermiculite is used alone, seedlings should be fed with a weak fertilizer solution when the first true leaves appear. A tablespoon of soluble fertilizer per one imperial gallon (3.78 : 1) of water is the recommended mix
- storing bulbs and root crops - pour vermiculite around bulbs placed in container. If clumps are dug, allow to dry for a few hours in the sun and then place in cartons or bushel baskets and cover with vermiculite. The absorptive power of vermiculite acts as a regulator that prevents mildew and moisture fluctuation during the storage period. It will not absorb moisture from the inside of stored tubers, but it does take up free water from the outside, preventing storage rot.
- soil conditionerSoil conditionerA soil conditioner, also called a soil amendment, is a material added to soil to improve plant growth and health. A conditioner or a combination of conditioners corrects the soil's deficiencies in structure and-or nutrients.-Purpose:...
- Where the native soil is heavy or sticky, gentle mixing of vermiculite up to one-half the volume of the soil is recommended. This creates air channels and allows the soil mix to breathe. Mixing vermiculite in flower and vegetable gardens or in potted plants will provide the necessary air to maintain vigorous plant growth. Where soils are sandy, mixing of vermiculite into the soil will allow the soil to hold water and air needed for growth. - as loose-fill insulationThermal insulationThermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...
- Exfoliated vermiculite treated with a water repellent is used to fill the pores and cavities of masonry construction and hollow blockwork to enhance fire ratings (eg. Underwriters Laboratories Wall and Partition designs), insulation and acoustic performance.Coarse grades of exfoliated vermiculite can be used to insulate lofts and attics. Exfoliated vermiculite has the benefit of being easy to use with application consisting of pouring the vermiculite between the joists and then levelling - Refractory/Insulation gunning and castable mixes - exfoliated vermiculite can be combined with high alumina (also known as calcium aluminate) cements and other aggregates such as expanded shale, clay and slate to produce refractory/insulation concretes and mortars. In the early days of their uses these products were batched at or very close to the place of installation, this continues to be the case in some limited circumstances, however more and more use is being made of pre-batched proprietary mixes. Mixes containing vermiculite are used in areas where strength and corrosion/abrasion resistance are of secondary importance, the most important factor being the insulation performance of the in place refractory lining. These mixes find their uses in such areas in industries including iron/steel, cement and hydrocarbon processing
- as a constituent of a coating - vermiculite dispersions are typically either chemically or physically very finely delaminated vermiculite in a fluid medium. These dispersions can be used to make vermiculite ‘paper’ sheet by simply pouring them on to a piece of smooth low surface energy plastic and allowing to dry, the resulting sheet can then be peeled off the plastic.Typical end uses for vermiculite dispersions include in high temperature coatings or binders for construction materials, gaskets, specialty papers/textiles, oxidation resistant coating on carbon based composites, and as barrier coatings for films.
- packing material, valued for its high absorbency
- Waste Treatment - the cation exchange capacity (up to 1000 milliequivalents per Kg) of vermiculite allows it to be used in fluid purification processes for waste water, chemical processing and the pollution control of air in mines and gases in industrial processes. In addition to its ion exchange properties exfoliated vermiculite will retain liquids within the inter-laminar voids of the individual particles as well as between the particles themselves.
- suitable as a substrateSubstrate (biology)In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
for various animals and/or incubationAvian incubationIncubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
of eggs - lightweight aggregate for plasterPlasterPlaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...
, proprietary concreteConcreteConcrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
compounds, firestopFirestopA firestop is a passive fire protection system of various components used to seal openings and joints in fire-resistance rated wall and/or floor assemblies, based on fire testing and certification listings....
mortar and cementitious spray fireproofingFireproofingFireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...
- Exfoliated vermiculite is used in both hand and spray applied general building plasters to improve coverage, ease of handling, adhesion to a wide variety of substrates, fire resistance, and resistance to chipping/cracking/shrinkage. - as an additive to fireproof wallboard
- component of the interior fill for firestop pillowFirestop pillowFirestop pillows are passive fire protection items, used for firestopping holes in wall or floor assemblies required to have a fire-resistance rating...
s, along with graphiteGraphiteThe mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal... - carrier for dry handling and slow release of agricultural chemicals
- growing medium for hydroponicsHydroponicsHydroponics is a method of growing plants using mineral nutrient solutions, in water, without soil. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as perlite, gravel, mineral wool, or coconut husk.Researchers discovered in the 18th...
. - ‘Hot Topping’ - both exfoliated and crude vermiculite have been used for ‘hot topping’ in the steel industry. When poured onto molten ‘hot metal’ crude vermiculite exfoliates immediately and forms an insulating layer allowing the material to be transported to the next production process without losing too much heat.
- means to permit slow cooling of hot pieces in glassblowingGlassblowingGlassblowing is a glassforming technique that involves inflating molten glass into a bubble, or parison, with the aid of a blowpipe, or blow tube...
, lampwork, steelworkIronworkIronwork is any weapon, artwork, utensil or architectural feature made of iron especially used for decoration. There are two main types of ironwork wrought iron and cast iron. While the use of iron dates as far back as 4000BC, it was the Hittites who first knew how to extract it and develop weapons...
, and glass beadmakingGlass beadmakingThe technology for glass beadmaking is among the oldest human arts, dating back 3,000 years . Glass beads have been dated back to at least Roman times... - used in in-ground swimming pools to provide a smooth pool base - Finer grades of exfoliated vermiculite plus portland cement may be combined either on site or a factory premix to provide a base for swimming pool vinyl liners. These mixes are either pumped into place using a rotor stator pump or hand poured.
- used in commercial hand warmerHand warmerHand warmers are small packets which are held in the hand and produce heat on demand to warm cold hands. They are commonly used in outdoor activities such as hiking and skiing to keep extremities warm and assist insulated clothing...
s - used as a sterile medium for the incubation of reptile eggs
- light-weight insulative concrete
- used in AGA cookers as insulation
- used in explosives storage as a blast mitigant
- used to absorb hazardous liquids for solid disposal
- used in gas fireplaces to simulate embers
- used as part of a substrate for fungi cultivation
Commercial manufacture of exfoliated vermiculite
British Geological Survey
The British Geological Survey is a partly publicly funded body which aims to advance geoscientific knowledge of the United Kingdom landmass and its continental shelf by means of systematic surveying, monitoring and research. The BGS headquarters are in Keyworth, Nottinghamshire, but other centres...
.
While some exfoliators focus on only a few of the possible applications, others can provide vermiculite products for all its applications. It is common for vermiculite exfoliators to exfoliate perlite also, as both are often sold together. For those who want to set up a new exfoliation process, it is possible to find expert consultants to advise in the design and construction of the desired facilities. Vermiculite exfoliators have an international trade association called The Vermiculite Association to represent the industry's interests and to exchange information. Many of its members also maintain memberships in The Perlite Institute.
Fireproofing
Sprays containing asbestos are still widely used for fireproofing in some parts of the world. These sprays contain aggregates of MMMF (man-made-mineral-fibres) including rockwool and ceramicCeramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
fibres. The cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
itious versions of these fireproofing sprays contain Portland cement
Portland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...
and lightweight aggregates
Aggregate (composite)
Aggregate is the component of a composite material that resists compressive stress and provides bulk to the composite material. For efficient filling, aggregate should be much smaller than the finished item, but have a wide variety of sizes...
of the plaster
Plaster
Plaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...
vermiculite. Vermiculite ore, particularly those mined from the U.S., usually is contaminated with asbestos. Danger of exposure to asbestos in these sprays is greatly increased when not handling following proper industrial hygiene
Hygiene
Hygiene refers to the set of practices perceived by a community to be associated with the preservation of health and healthy living. While in modern medical sciences there is a set of standards of hygiene recommended for different situations, what is considered hygienic or not can vary between...
procedures.
Asbestos contamination
Although not all vermiculite contains asbestos, some products were made with vermiculite that contained asbestosAsbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
until the early 1990s. Vermiculite mines throughout the world are now regularly tested for it and are supposed to sell products that contain no asbestos. The former vermiculite mine in Libby
Libby, Montana
Libby is a city in and the county seat of Lincoln County, Montana, United States. The population was 2,626 at the 2000 census.-Geography:Libby is located at , along U.S. Route 2....
, Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...
, did have tremolite
Tremolite
Tremolite is a member of the amphibole group of silicate minerals with composition: Ca2Mg5Si8O222. Tremolite forms by metamorphism of sediments rich in dolomite and quartz. Tremolite forms a series with actinolite and ferro-actinolite. Pure magnesium tremolite is creamy white, but the color grades...
asbestos as well as winchite and richterite
Richterite
Richterite is a sodium calcium magnesium silicate mineral belonging to the amphibole group. If iron replaces the magnesium within the structure of the mineral, it is called ferrorichterite; if fluorine replaces the hydroxyl, it is called fluororichterite. Richterite crystals are long and prismatic,...
(both fibrous amphiboles) — in fact, it was formed underground through essentially the same geologic processes as the contaminants. A vermiculite mine in Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
has also been found to be contaminated by asbestos.
Pure vermiculite does not contain asbestos and is non-toxic, but it can become contaminated over long periods if there is a presence of a secondary mineral called diopside
Diopside
Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms complete solid solution series with hedenbergite and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class...
. After millions of years of weathering, the biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
turns into vermiculite and the diopside turns into asbestos.
Controversy over health risks
The largest and oldest vermiculite mine in the United States was started in the 1920s, at Libby, MontanaLibby, Montana
Libby is a city in and the county seat of Lincoln County, Montana, United States. The population was 2,626 at the 2000 census.-Geography:Libby is located at , along U.S. Route 2....
, and the vermiculite was sold under the commercial name Zonolite. The Zonolite brand and the mine was acquired by the W.R. Grace Company in 1963. Mining operations at the Libby site stopped in 1990 in response to asbestos contamination. While in operation, the Libby mine may have produced 80% of the world's supply of vermiculite.
The United States government estimates that vermiculite was used in more than 35 million homes, but does not recommend its removal. Nevertheless, homes or structures containing vermiculite or vermiculite insulation dating from before the mid 1990s—and especially those known to contain the "Zonolite" brand—may contain asbestos
Asbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
, and therefore may be a health concern.
An article published in the Salt Lake Tribune on December 3, 2006, reported that vermiculite and Zonolite had been found to contain asbestos
Asbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
, which had led to cancers such as those found in asbestos-related cases. The article stated that there had been a "cover-up" by W.R. Grace Company
W. R. Grace and Company
W. R. Grace and Company is a Columbia, Maryland, United States based chemical conglomerate.The company has two main divisions, Davison Chemicals and Performance Chemicals. The Davison unit makes chemical catalysts, refining catalysts, and silica-based products that let other companies make...
and others regarding the health risks associated with vermiculite and that several sites in the Salt Lake Valley
Salt Lake Valley
Salt Lake Valley is a valley in Salt Lake County in the north-central portion of the U.S. state of Utah. It contains Salt Lake City and many of its suburbs, notably West Valley City, Murray, Sandy, and West Jordan; its total population is 1,029,655 as of 2010...
had been remediated by the EPA
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
when they were shown to be contaminated with asbestos. W.R. Grace Company has vigorously denied these charges.
The vermiculite deposit at the mine in Libby, Montana, was (and is) heavily contaminated with asbestos. Numerous people were knowingly exposed to the harmful dust of vermiculite that contained asbestos. Unfortunately, the mine had been operating since the 1920s, and environmental and industrial controls were virtually non-existent until the mine was purchased by the W.R. Grace Company in 1963. Yet, knowing the human health risks, the mining company still continued to operate there until 1990. Consequently, many of the former miners and residents of Libby have been affected and continue to suffer health problems. Over 200 people in the town have died from asbestos-related disease due to contamination from vermiculite mining from nearby Zonolite Mountain, where soil samples were found to be loaded with fibrous tremolite
Tremolite
Tremolite is a member of the amphibole group of silicate minerals with composition: Ca2Mg5Si8O222. Tremolite forms by metamorphism of sediments rich in dolomite and quartz. Tremolite forms a series with actinolite and ferro-actinolite. Pure magnesium tremolite is creamy white, but the color grades...
(known to be a very toxic form of asbestos), and countless others there who insulated their homes with Zonolite have succumbed to asbestos-related diseases, most of whom never were employed in environments where asbestos was an issue.
After a 1999 Seattle Post-Intelligencer
Seattle Post-Intelligencer
The Seattle Post-Intelligencer is an online newspaper and former print newspaper covering Seattle, Washington, United States, and the surrounding metropolitan area...
story claimed that asbestos-related disease was common in the town, the EPA
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
, in response to political pressure, made cleanup of the site a priority and called Libby the worst case of community-wide exposure to a toxic substance in U.S. history. The EPA has spent $120 million in Superfund
Superfund
Superfund is the common name for the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 , a United States federal law designed to clean up sites contaminated with hazardous substances...
money on cleanup. In October 2006, W. R. Grace Company tried to appeal the fines levied on them from the EPA, but the Supreme Court rejected the appeal. The United States government is also pursuing criminal charges against several former executives and managers of the mine for allegedly disregarding and covering up health risks to employees. They are also accused of obstructing the government's cleanup efforts and wire fraud. To date, according to the indictment, approximately 1,200 residents of the Libby area have been identified as suffering from some kind of asbestos-related abnormality. Jury selection was to have been completed in February, 2009.
The case ended in acquittals on May 8, 2009. On June 17, 2009, the EPA issued a public health emergency in and near Libby, thereby allowing Federal agencies to provide funding for health care, and for removal of contaminated insulation from affected homes.
See also
- Passive fire protectionPassive fire protectionPassive fire protection is an integral component of the three components of structural fire protection and fire safety in a building. PFP attempts to contain fires or slow the spread, through use of fire-resistant walls, floors, and doors...
- FireproofingFireproofingFireproofing, a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a...
- FirestopFirestopA firestop is a passive fire protection system of various components used to seal openings and joints in fire-resistance rated wall and/or floor assemblies, based on fire testing and certification listings....
- AsbestosAsbestosAsbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
- PerlitePerlitePerlite is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently...
- Sodium silicateSodium silicateSodium silicate is the common name for a compound sodium metasilicate, Na2SiO3, also known as water glass or liquid glass. It is available in aqueous solution and in solid form and is used in cements, passive fire protection, refractories, textile and lumber processing, and automobiles...
- PlasterPlasterPlaster is a building material used for coating walls and ceilings. Plaster starts as a dry powder similar to mortar or cement and like those materials it is mixed with water to form a paste which liberates heat and then hardens. Unlike mortar and cement, plaster remains quite soft after setting,...
- List of minerals
- Square foot gardeningSquare foot gardeningSquare Foot Gardening is the practice of planning small but intensively planted gardens. The phrase "square foot gardening" was popularized by Mel Bartholomew in a 1981 Rodale Press book and subsequent PBS television series. A full-length companion DVD, Square Foot Gardening , was recently released...
External links
- The Vermiculite Association
- Cornell Boodley and Sheldrakehttp://www.greenhouse.cornell.edu/crops/factsheets/peatlite.pdf
- US Geological Survey Vermiculite Section
- Environmental Working Group
- United States Environmental Protection Agency
- The Perlite Association http://www.perlite.org/
- Petition for writ of certiorari to U.S. Supreme Court (April 27, 2006)