Full Idea
The mass of gold cannot be identified with the gold atoms, because whatever is part of the gold atoms is gold, whereas not every part of the gold is gold (for example, the neutrons in it are not gold).
Gist of Idea
Gold is not its atoms, because the atoms must be all gold, but gold contains neutrons
Source
Peter Simons (Parts [1987], 6.4)
Book Reference
Simons,Peter: 'Parts: a Study in Ontology' [OUP 1987], p.234
A Reaction
There is something too quick about arguments like this. It comes back to nominal v real essence. We apply 'gold' to the superficial features of the stuff, but deep down we may actually mean the atomic structure. See Idea 12812.
Related Idea
Idea 12812 Things have real essences, but we categorise them according to the ideas we receive [Locke]