Palmierite (and atacamite?)

[Jorge_Stolfi]

How does a random reference to the Voynich end up there? Probably taken from the Wiki..

Yes, that is one of many sites that repackage Wikipedia articles.  "LLMs before LLMs"...

I wonder with minerals like these, do they have to come from a natural deposit?

The Wikipedia article lists a reference that gives a little more information:

• "Palmierite is a rare fumarolic sublimate occuring at a handful of localites worldwide. It is a lead sulfate. According to the old Cureton tag this is from the eruption in 1924. The yellow [in the photo] is perhaps some sulfur or one of the many sulfates such as Erythrosiderite or Metavoltine. The Palmierite are tiny colorless plates as is the Aphitalite. Vesuvius complex contains an incredible 39 type locality minerals, this being one of them."
  

Thus, apart from the extreme rarity, inaccessibility, and recent date of discovery, no one would think of using palmierite as a pigment.

can trace amounts be explained by some chemical processes taking place during ink preparation, with contaminants etc?

The chemical formula is very simple and I would not be surprised if traces of it it can form if the elements are present.  But just saying "palmierite detected" without discussing this point is by itself quite misleading.  We can see the confusion that it caused, including that spurious reference in Wikipedia.

And, again, the "detection" is very likely to be just a false match.  

All the best, --stolfi