Allied with Crystal Healing (See 14/1/19), woo-practitioners have ascribed meanings and properties to specific crystals. For instance according to Crystalearthspirit.com, Fluorite "draws away negative energy and stress, cleansing and purifying the body", whereas Healingcrystals.com says "Fluorite absorbs negative energies from the environment and is effective at Auric and Chakra cleansing" and Science says it is "is the mineral form of calcium fluoride, CaF2" and useful in optics.
Undoubtedly very old the practice was limited to those common crystals that were unknown, or at least unclassified, until science came along and discovered their properties. Since then new-age spiritual type business people have been ascribing different properties in the hope of selling ever more ludicrously overpriced crystals until the industry settled on a rough conformity of meanings. Fluorite, for instance is claimed to "promote focus, intuition and understanding. It helps to bring chaos into order, promoting stability, free thinking and clear unbiased reasoning". Clearly not very successful at doing so.
During the Fringe, we offered our audiences our skeptical healing crystals to anyone who donated £5 at our talks. They seemed to go down very well and we ended up having to buy more to meet demand. Given that new-agers ascribe meaning to them we thought we should do likewise. See here for the different types.