Is Zakat obligatory on 100 grams of gold owned through a gift by a 15-year-old, or on the amount exceeding 85 grams of it, especially since he has no private money?

Zakat is obligatory on gold that reaches the nisab (minimum threshold) and a full hawl (lunar year) has passed on it, which is 100 grams. The amount of Zakat due is two and a half grams (a quarter of a tenth). However, if the gold is in the form of jewelry, there is no Zakat due on it according to the majority of scholars. Zakat becomes obligatory on the owner, even if they are a child, provided the conditions for Zakat are met. The principle is that Zakat should be paid from the same type of wealth.