Alms Tax: Annual Zakat on Gold and Silver
Practical Laws of Islam as per the teachings of Ayatullah Sistani
Ruling 1914
If the gold or silver that someone owns has reached the niṣāb, then even if he has given zakat on it he must continue giving zakat on it every year as long as it does not fall below the niṣāb.
-Ayatullah Sistani, Practical Laws of Islam, Alms Tax (Zakat)