It is when the particles in the air settle down in the gold and deposit impurities that it gets the color gold. So the purest gold you can get 12k, 18k, 24k it doesn't not matter, it is imperfect and will never be pure. The streets of the new Jerusalem are made of pure gold. As we are to be in our walk with God we should be like pure gold, invisible to us, only visible of Him. As gold is refined so are we.
Gold is heated to a certain temperature and then cooled.
Each time more and more of the worldly things such as dust and so on are refined out, and the Gold becomes closer and closer to purity. Others who are walking as the world, judging or in judgment of others will be like those in Matthew 7 Matthew 7 1. Judge not, that ye be not judged. We need to learn to be invisible so the love of God can show through us. Also if God is in you and you are pure as pure gold you won't have to worry what any one sees because they will see right through you to God.