Is this rule exclusive for partitive articles?

Bonjour Anish, This is the lesson statement that most aptly fits your question: ATTENTION: This rule does NOT apply to sentences using the verb être, with which the partitive article doesn't change. C'est du sel de Guérande ? -Non, ce n'est pas du sel de Guérande. Is that Guerande salt? -No, it's not Guerande salt. C'est de l'huile d'olive ? -Non, ce n'est pas de l'huile d'olive. Is this olive oil? -No, this is not olive oil. J'espère que cela vous aidera. Ron