Hi Lucien,
I have looked at the pictures several times and cannot see clearly what you mean by the white stain. Perhaps you can post a better picture here.

In the meantime, if the white stain can be easily washed off with soap and water then I would guess it is mold, mildew, or perhaps residue from the old cardboard box that the beads were stored in. If the stain does not wash off, then we need to see a good close-up picture to go further.

Welcome to the forum!

look just below the label for a bead with whitish stuff on it. Rather than mold as in the growth in a damp climate, I think Lucien is referring to the mold used in making the beads. And I don't think this is it either. I have seen this effect before, but can only surmise it must result from some impurity in the glass that happens to be on the surface of the bead, and then due to the irregular surface, sediment of some material present in the finishing process?

Had a look at them before, trying to find the stains. At first I thought the reflection was giving white spots in the image. When looking closer, I do indeed see some white spots on a few beads.

These beads are quite a common type of Czech beads, made to resemble garnet. I have not seen stains like this on them before. It is a clear glass, and not very prone to impurities. The molding process does not really make stains like this, not in a clear uniform glass. I can imagine it is some type of damage done by water with a high calcium content (lime scale), but then I would imagine the label and the thread to also be affected by the water. Same goes for any type of mold that could grow under damp conditions.

So basically, I have no idea. Perhaps someone spilled paint on them? Or some type of paint/glaze used on other beads got splattered?