What kind of wall insulation is this? The house was build in

>>1228375
Looks like mineral wool aka rockwool. Could also be a fiberglass/wool combo (real wool, like off of a sheep) that I have seen in houses of that vintage.

>>1228380
Any chances of it being contaminated with asbestos fibers?

>>1228386
It is unlikely but not unheard of. Get it tested if you are worried.

Holy shit OP I was just dealing with this, exact same situation (60's house and found unfamiliar insulation that turned out to be rockwool). I was lucky that mine actually still had legible paper with it that clearly said "rock wool".

Yours looks identical to mine. From what I understand in my research the only asbestos-containing rockwool either has trace amounts or has clear asbestos layers embedded in it. If all you have is just brown mass of fibers then you're fine.

Also keep in mind asbestos is bad to breathe, but a few minutes of exposure isn't going to give you cancer. The reason it's been banned is because installers and occupants were both bound to have repeated, long-term exposure, which is what causes problems.