What is the requirement regarding the type of wealth from which Zakat must be paid?

Primary text

Zakat must be paid out of the same genus (kind) of wealth owned. If the wealth consists of different types of equal value, it is permissible to pay Zakat from any one of those types, analogous to paying from one of two types of sheep. If the values differ, the payment must be taken from each type proportionately. It is permissible to pay from the intermediate quality wealth if it covers the due amount and value. Furthermore, paying from the best quality wealth, in an amount sufficient to cover the obligation, is permissible, and the payer receives the reward for the excess given.