You may have come across it in between the floor joists of your attic, or in between the studs of your walls - a lightweight, granular material that looks a bit like gravel, but seems almost as light as air.
Cashins & Associates Blog
For much of the 20th century, asbestos was viewed as the "miracle mineral" due to its various desirable properties. It was fire-resistant, non-corrosive, chemical-resistant, and made a great insulator. Further, it could be added to just about anything. Industrialization of the mining process allowed for asbestos fibers to be ground so small that the mineral could be sprinkled into anything from joint compound to cigarette filters.