Why the Refinery?

What does the word "refine" mean?

To reduce to a pure state, to free from moral imperfection, to improve or perfect by pruning or polishing, to free from what is coarse, vulgar, or uncouth, to become pure or perfected, to give distinctions, from from impurities. "Refinery" is a building and equipment for refining, like sugar, to make pure and sweet.

... I will refine them like silver and test them like gold. They will call on my name and I will answer them; I will say, "They are my people,' and they will say, "The Lord is our God.'" Zechariah 13:9