Answer:
That black, sooty-looking substance on the skins of onions is indeed a mold, specifically, Aspergillus niger. It is common on onions, both in the field and once dried, bagged and stored. The fungus typically is found on the outside skins of an onion, and it is harmless, for the most part.
So you know that your measurements are exactly correct.
Answer:
Mold fossils A fossilized impression made in the substrate; a negative image of the organism.
Cast fossils Formed when a mold is filled in.
Trace fossils or Ichnofossils Fossilized nests, gastroliths, burrows, footprints, etc.
True form fossils Fossils of the actual animal or animal part.
