How do you tell the difference between ink particles and mold?

Obligatory no images because I cleaned everything and threw away the offending sample before even thinking about it. I also know mold gets way overstated here and I’m not trying to add to that if it isn’t that. I just haven’t seen any comprehensive guides posted to tell the difference.

I’d filled a pen from a sample of Monteverde color changing blue to neon yellow

There was no visible oddness in the sample until after I inked it, (nothing floating on the top, ect) and it smelled like usual. I saw little dark particles in it when I put it on paper. They somewhat dissolved in water, but left behind little dark specks. It seemed like these particles clung to the sample vial as well. I don’t think I could’ve gotten photos if I’d tried. I don’t really expect that information to get me any confirmation of mold or not, but I’d like to know for the future.