I have a 1930 house in Toronto, Canada with a strange attic insulation that no one seems to know what it is. It appears to be light cement material that was poured in place wet between the ceiling joists and in the spaces that access the soffits and dried to fill the spaces. It breaks up easily into large chunks and contains air bubbles much like an Aero chocolate bar. The only similar product that I have found is Air Krete, but Air Krete apparently wasn't available in Canada until 2005. We had it tested at the lab for asbestos, it does not contain asbestos fibers and was described as a "grey, soft, cementious material."
There is old cellulose on top of this material. It may have been installed after the house was built.
There are lightweight insulating cellular concretes that are used on roof decks and other places. They are pumped in place and screeded. They sort of have the consistancy of whipped cream before they cure. They can vary a lot in density and don't typically have really good R values. Maybe somebody got the idea to use it in the attic.