Mystical Crystals author Cerridwen Greenleaf has written a blog post on the symbolism of chains.

Chains represent links between people, the ties that bind you to another. Other mystical associations for chains are happiness and justice; prayer; reason and the soul; communication and command. Plato referred to a chain of being, a golden chain linking the earth to the heavens above, a bond between humans and immortals. Socrates tied our human happiness to the concept of justice with a chain of steel and diamonds. Pseudo-Dionysius the Areopagite compared the practice of prayer to an infinitely luminous chain going from Earth to heaven. An astral cord, akin to a golden chain, binds the spirit to the psyche and binds reason to the soul.
mystical crystals
Magical Stones and Gems for Health, Wealth, and Happiness
With information on stones for each area of life, including love, work, home, and stress-busting, The Crystal Companion is a beautifully illustrated guide to using crystals and gemstones to channel positive energy into all areas of your life that need special attention. With chapters like “Birthstone Secrets: Discovering Your 4 Soul Stones,” “Tranquility Touchstones: Stress-Reducing Rocks,” and “Crystal Charms: How to Choose and Make Change-Your-Life Jewelry,” there something for both the beginner and the more knowledgeable in Greenleaf’s latest book.