Is zakat obligatory on African gold and gold-plated metals, and is its amount the same as that of regular gold?

Pure gold is subject to Zakat if its conditions are met, whether it is African or not, and whether it is of good or poor quality. As for gold mixed with other substances, Zakat is not obligatory on it until its pure gold content reaches the nisab, because what is mixed with it is not currency and is not subject to Zakat. Therefore, whoever owns mixed gold must determine the amount of pure gold within it. If it reaches the nisab, Zakat becomes obligatory on it, and the other metals or stones mixed with it, which are not subject to Zakat, are not included in the calculation.