"Is it mine?"
Translation:Is het van mij?
No, this does not work. However, one could say "Is het de mijne?". Here de mijne is a possessive pronoun meaning mine. The phrase "Is het van mij" could be literally (and awkwardly) translated as "Is it of me?".
There is a slight difference in meaning between these two translations. "Is het de mijne?" uses the determinate article de, so it points to a specific object and it assumes that everyone in the conversation knows this object is mine. A more precise translation would be "Is it the one that is mine?".
I like 'Is het van mij'' better. I think it is more general, but your solution is not wrong. You could think of a situation where someone says that something belongs to you: 'het is van jou', after which you would repeat "Het is van mij?'' to ask for confirmation, or to make sure you understood the other one correctly. I hope that makes sense.