Butyl rubber insulation but as in previous post, weave could be asbestos.
These days most countries have facility for testing @ maybe $40. Sample is placed in a tough plastic bag and results come back about a week later.
I have doubts on the effectiveness of a paper mask also.
This can be seriously dangerous and I for one, would give it a wide berth.
Also be aware there are many other sources where asbestos hides in old houses, wall sheeting, floor covering, switchboards and as we recently found, the old bakolite switches.