What is the ruling on zakat for gold mortgaged for personal use, and upon whom is the zakat obligatory: the mortgagor or the owner of the gold?

In Islamic law, a mortgage (rahn) is money designated as security for a debt, to be recovered from its value if the debt cannot be obtained from the debtor. If "mortgaged gold" is what is meant, then according to the view that zakat (definition) is obligatory on jewelry intended for use, zakat becomes obligatory on mortgaged gold, provided its conditions are met (owning the minimum taxable amount and the passing of a full year). Its zakat is obligatory upon its owner (the sister asking the question), not upon the mortgagee, because the mortgagee's possession is one of trust, not ownership.