Based on Chapter 19, describe the true nature of the Soul and how it remains unaffected by the material world, using the analogies provided.

Chapter 19 teaches that the Soul is distinct from the body, senses, mind, and life-force; it is self-luminous, pure consciousness, changeless, and formless. Though it appears in the world due to the actions of Maya, it remains untainted. The text uses the analogy of a crystal, which appears red or yellow depending on the color near it, yet remains pure, distinct, and free from change itself. This chapter further explains that the ego of 'I am the body' is a false bondage, similar to mistakenly perceiving a snake in a coiled rope or seeing the glitter of silver on a seashell—it is a superimposition that is not real.