What is the standard purity of silver to be considered in calculating the Nisab, if gold is calculated based on 24-karat purity?

Zakat is obligatory on pure and mixed gold and silver if they reach the nisab (minimum threshold) and a hawl (one lunar year) passes over them. However, only the pure amount is subject to zakat. The nisab for pure gold (24-carat) is 85 grams, and for pure silver (1000-grade) is 595 grams. The criterion is reaching the nisab, regardless of the carat. The nisab can be determined by asking experts about the price of one gram of pure silver.