Are white edges on attic floorboards mold?

There are white marks on the wooden floorboards in the attic.

The chimney was leaking and water got in. The white marks were already there before. Now of course we don’t know if water had already gotten in before and we didn’t notice it.
Can it be seen if this is mold?

From a distance, it is hard to say. Is the wood damp? Does it smell musty? Have you ever checked with a moisture meter? Possibly dismantle a plank and look underneath. There are also inexpensive mold tests available, which at least allow a statement about whether it could be mold or not.

The white edges were already there before. Now, of course, we don’t know if water had already gotten in before and we didn’t notice it. Is it possible to tell if it’s mold?

Before I think of mold, I think of lime, saltpeter, some kind of salts. What should one tell from what? To what extent do people think of mold when seeing white edges? Mold is black, unless we’re talking about white cheese mold. Why should one think of mold now when the supposed indicators were already there before? Why isn’t the paneling simply opened up, that’s the most obvious thing to do when there are concerns about penetrating moisture. Yes, and then a remote diagnosis in a house-building forum is of course not meaningful at all, whether or not. For that, there are laboratories that do analyses.