Geologist Dr. James Clark recounts visiting the Soviet Union a few years after Communism dissolved. He was asked to preach at a small Russian Baptist church that lived through a long season of persecution. Some in the congregation had been in prison because of their testimony in Christ. Others had husbands or relatives that had suffered or had even been killed for their faith. Dr. Clark decided to use the following geological illustration:

Clay is actually composed of many microscopic clay mineral crystals, which not even a light microscope can see. But under pressure the clay minerals are not crushed or made smaller. Rather, they grow larger. The minerals change into new larger biotype grains forming slate, found on many homes. With even more pressure, the minerals become even larger. And some are transformed into garnets, which are semi-precious gems.

Clark said:

I explained to the congregation that this geological process illustrates how pressure and suffering can be used to refine, purify, and mold a person into a more beautiful soul. I will never forget what I saw when I looked at the congregation. It seemed like the whole congregation was sparkling. The babushkas' (old women) eyes were gleaming bright with tears recalling past suffering. What makes a gem so attractive? It's the reflection. And these dear women and men were reflecting God's glory through the suffering they had endured.

The metamorphic rock story doesn't end there. With even more pressure applied, a new mineral forms called staurolite. The name is from two Greek words meaning "stone cross." The twin variety forms deep under high mountains in the shape of a cross. A reminder of Christ's ultimate suffering for us all.