'Refining' in the Bible

The refining pot is for silver and the furnace for gold,But the Lord tests hearts.

The refining pot is for silver and the furnace for gold [to separate the impurities of the metal],And each is tested by the praise given to him [and his response to it, whether humble or proud].

The bellows blow fiercely,The lead is consumed by the fire;In vain they continue refining,But the wicked are not separated and removed.