Is zakat obligatory on diamonds? What is the wisdom behind not obligating it on other precious stones, which may exceed gold and silver in value, even though some scholars are of the opinion that zakat is not obligatory on jewelry and precious stones except for gold and silver?

Diamonds and precious stones are not subject to Zakat if they are for adornment or saving, not for trade, because Zakat is obligatory on growing wealth. Gold and silver jewelry are not subject to Zakat, according to the majority of scholars, if they are for personal use only. However, if they are for trade or saving, Zakat becomes obligatory on them under certain conditions.