"Trials teach us what we are; they dig up the soil, and let us see what we are made of." - Charles Spurgeon
Most crucibles are made of graphite. This affords them the ability to withstand enormous heat; melting any material inside. After the gold has been taken through the painful process of breaking, by the refiner, the next stage is; The Crucible
The refiner puts the broken, crushed, unrefined ore into a “crucible”; a fireproof MELTING pot able to withstand great heat. The crucible goes into the furnace - a device used for extraction of metals from ore in refineries, and chemical plants. It's a heat source - which has enough heat necessary for expulsion of other metallic impurities undermining the quality of the gold.
Just as the furnace is used to purify gold in the crucible, God, our refiner, uses heat to purify us. You'll note that, the refiner doesn't just throw the gold into the furnace. He
