How can one pay Zakat on gold for the past ten years, knowing that it was a gift, was not worn, and there was no intention of selling it?

Scholars have differed regarding the zakat (definition) on jewelry intended for wear. The fatwa (definition) we follow is that there is no zakat on it as long as it is intended for wear.

However, according to the view that mandates zakat on it, it is not obligatory unless it reaches the niṣāb (85 grams). If it reaches the niṣāb and you wish to pay its zakat as a precautionary measure, then for each year, you should pay 2.5% of the gold itself, or 2.5% of its value for that year.