[pfix]

Wikipedia says yes: https://en.wikipedia.org/wiki/Basalt_fiber

> The basalt fibers typically have a filament diameter of between 10 and 20 μm which is far enough above the respiratory limit of 5 μm to make basalt fiber a suitable replacement for asbestos.

The source mentioned is a basalt fiber brand website, so not sure if that's enough for confidence.

[p0w3n3d]

but still it breaks and gets airborne...

[0_____0]

So does fiberglass. I would dislike working with the aforementioned basalt fiber, I suspect it's like fiberglass or carbon fibers in that you'll end up itchy later, unless you do a really good job with your PPE e.g. taping gloves to your sleeves.

[ahartmetz]

This still seems iffy, but... broken fibers usually become shorter, not thinner.

[tokai]

This is the exact way of behaving that facilitate conspiratorial thinking. You could have looked into it. Found sources that covers harmful effects of stone wool. Instead this 'just pointing out' that it might be problematic is lazy, dumb, and potentially destructive.