What are prayer & meditation? activities that allow humans to purify everything within their heart & soul, until they become as limpid as gems

Gems - symbol of the inner work human beings can achieve

"If life, light and celestial currents are to come through, you have to make way for them. This law is pointed up by everything in nature. Why are gems so valued? Because they let the light through... And if nature has succeeded in doing such magnificent work on certain minerals, in refining, purifying and colouring them, turning them into the marvels we admire today - crystals, diamonds, sapphires, emeralds, topazes, rubies, and so on - why would human beings not be capable of doing the same work within themselves?
What are prayer and meditation? Precisely those activities that allow humans to purify and illumine everything within their heart and soul, until one day they become as limpid as a gemstone. Then, the Lord, who appreciates gemstones very much, will set them in his crown. It is an image, of course, but it corresponds absolutely to a reality."