Asbestos is a naturally occurring silicate mineral that separates into fine, strong, flexible fibres. Those fibres do not burn, do not rot, resist most chemicals, insulate against heat and sound, and reinforce whatever they are mixed into. It was cheap, it was abundant, and it made cement stronger, ceilings quieter and boilers safer. That is why it is in almost every British building of a certain age, and why nobody thought twice about it for a century.
The properties that mattered
Fire resistance, which put it into flues, fire protection, textiles and boards. Thermal and acoustic insulation, which put it into lagging, sprayed coatings and ceiling tiles. Tensile strength, which put it into cement products, roofing sheets and pipes. Chemical resistance, which put it into gaskets and seals. And low cost, which put it into everything else.
The three types in British buildings
Chrysotile, the white one, overwhelmingly the most used and the last to be banned. Amosite, the brown one, in insulating board and some insulation. Crocidolite, the blue one, in sprayed coatings and lagging. Three others, anthophyllite, tremolite and actinolite, were regulated too and appear mainly as contaminants rather than as products.
Why the same properties make it hard to remove
The fibres are fine enough to stay airborne for a long time, strong enough not to break down, and durable enough not to degrade once inhaled. That is the same durability that made it a good building product. It is why removal is done wet, under enclosure where the material is friable, and why a clearance is measured rather than judged.
What the properties do not tell you
Nothing about a specific material in a specific building. Asbestos cement and sprayed coating share a mineral and behave completely differently, and the regulations follow the product and the work rather than the mineral. The type on an analysis certificate is a fact for the register, not an instruction.
Questions people ask about properties of asbestos
How many types of asbestos are there?
Six were regulated; three account for almost everything in a British building: chrysotile, amosite and crocidolite.
Is asbestos man made?
No. It is a group of naturally occurring silicate minerals that were mined and processed, which is why contamination of other minerals from the same ground, such as some vermiculite, is a real issue.
Why is it still in buildings if it was banned?
The ban stopped new use. Material already installed was not required to be removed, and the law is built around managing it in place.