Is this fiberglass insulation?

Question

I'm having a difficult identifying the type of insulation behind a section of drywall. The home was built in North America around the 1940s. It's undergone several rounds of renovation projects and there's evidence of building materials from the '40s, '60s, '90s, and the early aughts.

I've looked through some photos over at Inspectapedia's insulation identification page. After looking closer at the fiberglass identification page I did see the following image which bears some resemblance to the insulation in question (please the second and third images). However, I have no experience identifying insulation and I'd like the feedback of those who are more experienced.

I plan to install an electrical receptacle on the stud here. I'll need to accommodate for the insulation while doing so in a safe manner. I won't hold anyone liable for opinions shared, and I will use PPE when interacting with the insulation either way.

Photo 1: Inspectapedia fiberglass reference image.

Photo 2: Unidentified greenish/desauturated insulation in home behind drywall. Closeup with flash on.

Photo 3: Unidentified greenish/desauturated insulation in home behind drywall. Taken at arms length with flash off.

Answer 1

Based on Photo 3 that looks very much like Rockwool insulation. Not sure if that's an actual trademark or just a common trade name, but that's the link to what appears to be an "official" site about it.

As I understand it, this stuff cuts very cleanly - I think you'd use a smooth edged knife (like a utility knife), not a serrated knife (like a drywall knife). You'll want to cut out a hole for the new box to go in, not compress it behind.

Answer 2

This looks like mineral wool insulation, and not fiberglass, the pattern on the top of the batting is the giveaway. Generally mineral wool batting between studs is semi-rigid, and not as loose as paper backed fiber glass batting (aka, the pink stuff).