They find pearls on their coasts, and diamonds and carbuncles on their rocks; they do not look after them, but, if they find them by chance, they polish them, and with them they adorn their children, who are delighted with them, and glory in them during their childhood; but when they grow to years, and see that none but children use such baubles, they of their own accord, without being bid by their parents, lay them aside, and would be as much ashamed to use them afterwards as children among us, when they come to years, are of their puppets and other toys. –Utopia,
Thomas More

How do the details about how the Utopians treat valuables develop the central idea?

They provide an example of how valuables are found, treated, and traded.
They state facts about different uses for valuables.
They make an analogy between children outgrowing playing with valuables and children outgrowing playing with toys.
They give an anecdote about a time when these valuables were found and used for the good of the community.