Why is gangue sometimes reprocessed.

To win some of the ore associated with them as they can become more economical to produce.

Explanation:

Sometimes gangues are reprocessed so as to win back some of the ore that are associated with them as they become more economical to produce if the price of the metal goes up.

Gangues are undesired minerals that occurs in association with the desired ore. They are usually treated as wastes in mining.

Often times, gangues can become economical to mine. Some gangues are not totally wastes, they are just undesired materials associated with the ore. Under certain economic considerations, they might become economical and augment the ore being processed. The price of the metal determines if the ore in the gangue should be won.