Looking at the “floor” of an attic in an older house that was insulated between 1919 and the late 50’s you might see a granular material with a silver/ whitish colors where you expected to see fiberglass insulation.
If you are looking at buying or are living in a home with this stuff you need to know what it is and it’s potential dangers.
The answer to the question is: Vermiculite insulation.
This insulation may have an asbestos content which is greater than 1% which has been determined to be dangerous to your health if dust/fibers are inhaled. Most of this type of insulation is not dangerous but determining that requires sending it to a laboratory to be tested.
This insulation mostly sold under the Zoelite brand was produced up to the late 1980’s, but not used much in our area after the late 50’s