Since I am giving a lot of details about the physical and metaphysical properties of gemstones, I thought it is important to let you know the initial sources from where the information comes from. So here I will list down the main sources for your reference.
But it is important to know that some of the knowledge and believes about gemstones are coming from generation to generation by word of mouth. A part of this knowledge is properly documented and some parts are not. Since it is not a tangible subject, science has also proved only some aspects.
It is up to you to read the information and decide whether to believe or not.
[Simmons, pp.] Robert Simmons & Naisha Ahsian, The Book of Stones (Berkley, CA: North Atlantic Books, 2007).
[Schumann, pp.] Walter Schumann, Gemstones of the World
[Hall, pp] Judy Hall, 101 Power Crystals (Beverly, Fair Winds Press, 2011)
[Megemont, pp.] Florence Megemont, The Metaphysical Book of Gems and Crystals (Rochester, VT: Healing Arts Press, 2008).
[Kunz, pp.] George Frederick Kunz, The Curious Lore of Precious Stones (New York: Dover Publications, 1971).
[Eason, pp. ]Cassandra Eason, The New Crystal Bible (London: Carlton Books Ltd., 2010).
[Hall, pp.] Judy Hall, The Crystal Bible (Cincinnati, OH: Walking Stick Press, 2003).
[Hall 2, pp.]Judy Hall, The Crystal Bible 2 (Cincinnati, OH: Walking Stick Press, 2009).
[Mella, pp.] Dorothee L. Mella, Stone Power II (Albuquerque, NM: Brotherhood of Life, Inc., 1986).
[Ahsian, pp.] Robert Simmons & Naisha Ahsian, The Book of Stones (Berkley, CA: North Atlantic Books, 2007).
[Melody, pp.] Melody, Love Is In The Earth (Wheat Ridge, CO: Earth-Love Publishing House, 1995).
[Raphaell, pp.] Katrina Raphaell, Crystal Enlightenment (Santa Fe, NM: Aurora Press, 1985)
[Fernie, pp.] William T. Fernie, The Occult and Curative Powers of Precious Stones (Blauvelt, NY: Rudolph Steiner Publications, 1973).
[Gienger, pp.] Michael Gienger, Healing Crystals (Scotland: Earthdancer Books, 2009).