Asbestos is a mineral that forms in nature. It develops in certain rocks when the rock is altered by heat, pressure and water and some of the minerals crystallise into thin fibres. Asbestos ended up in homes when such fibre deposits were mined and the fibres were mixed into fillers, adhesives, boards and insulation. So at home you almost always come across asbestos in industrially manufactured building products, not in natural stone.
In this article we explain which rocks asbestos forms in, where it was mined, what role the bedrock plays and what asbestos in nature means for you if you live in or want to renovate an ordinary home.
How does asbestos form in nature?
Asbestos is not a single substance but a collective term for six silicate minerals that can crystallise in fibrous form. Special conditions are needed for fibres to form. This usually happens when rock deep in the Earth's crust is altered by heat, pressure and circulating fluids. The fibres often grow in cracks and veins in the rock, where they can separate into bundles.
- Serpentine asbestos, i.e. chrysotile, forms in serpentinite, a rock altered from magnesium-rich rock. Chrysotile fibres are curly and flexible.
- The amphibole asbestos types, i.e. amosite, crocidolite, anthophyllite, tremolite and actinolite, form in altered rocks, and their fibres are straight and stiff.
The differences between the groups are described in more detail in the article Serpentine and amphibole asbestos, and what counts as a fibre in the article Asbestos fibre.
The same mineral can be a fibre or ordinary rock
Most asbestos minerals also occur in nature in non-fibrous form. Tremolite, actinolite and anthophyllite, for example, are common minerals in many rocks, and they usually occur as crystals rather than fibres. A mineral only counts as asbestos once it has crystallised into thin fibres. That is why the name of the rock or mineral alone does not tell you whether it is asbestos.
Where was asbestos mined?
Economically significant asbestos deposits exist in only a few places, and world production was concentrated in a small number of countries. Chrysotile was by far the most widely mined type of asbestos, and among the largest producers were Canada and the Soviet Union. Chrysotile was used, among other things, in asbestos cement sheets. Amosite was mined mainly in South Africa, and crocidolite in South Africa and Western Australia.
Tremolite and actinolite were generally not mined as asbestos. They ended up in products mainly as a contaminant together with other minerals, for example in chrysotile, vermiculite or talc, because they occur in the same rocks in nature.
Asbestos in the bedrock
In some places there are rocks in which asbestos minerals occur naturally. In intact bedrock the fibres remain enclosed in the rock. This only becomes relevant when such rock is quarried, crushed or drilled, because fibres can then be released with the dust. That is why naturally occurring asbestos is taken into account, for example, in the production of crushed stone and aggregate and in mining.
Some countries also mined their own asbestos, for example anthophyllite. You can read more about this type of asbestos on the page Anthophyllite.
Is natural asbestos dangerous at home?
In everyday life at home you generally do not need to worry about natural asbestos. The asbestos risk at home is almost always linked to old building products to which fibres were deliberately added: filler, tile and floor adhesives, asbestos cement sheets, pipe insulation and vinyl floor tiles. These are described in the article Where can asbestos be found?.
The health risk is the same regardless of where the fibre comes from. All types of asbestos cause cancer, and the danger arises when fibres get into the air you breathe. Intact material or intact rock does not release fibres. If you are worried that you have been exposed, talk to your doctor or your occupational health service.
How does the laboratory tell asbestos apart from other fibres?
Because the same mineral can be a fibre or ordinary rock, and because there are also many other fibrous minerals in nature, asbestos cannot be identified by its appearance. Semlab examines samples with a JEOL SEM-EDS electron microscope in accordance with ISO 22262-1. The microscope image shows the shape of the fibre, and the elemental analysis shows its chemical composition. Together they distinguish the six asbestos minerals from one another and from other fibres such as glass wool and rock wool.
What should you do if you suspect asbestos in a material at home?
If the renovation involves material installed before asbestos was banned in your country (2005 at the latest across the EU, and earlier in many countries), have it tested before it is sanded, drilled or demolished. You can take the sample yourself:
- Wear disposable gloves and a respirator of at least class FFP3.
- Moisten the sampling spot with a spray bottle to keep dust to a minimum.
- Remove a piece of about 2–5 centimetres so that all layers down to the base come with it.
- Put the piece in a resealable plastic bag, seal it and place it in a second bag.
- Write the sampling location and the material on the bag.
- Cover the sampling spot with tape and wipe the surface with a damp cloth.
You will find more detailed instructions in the article How to take an asbestos sample. You receive the result by email, usually on the same day the sample arrives at the laboratory. If asbestos is found, the demolition must be carried out by a specialist asbestos removal contractor.
How much does an asbestos analysis cost?
The analysis costs €49.99 incl. VAT per sample. The price is the same for 1–100 samples. Postage is not included. You can order the analysis online, pay by card and send the sample as a letter or small parcel with your national postal service to the laboratory in Finland.