Rock Crystal is the name given to all clear colorless quartz. It is widely used as a popular ornamental stone and is also used as a gemstone. Although it is one of the least expensive gemstones, cut rock crystal has been used as imitation diamonds. Rock crystal lacks the fire, color (of course) and the rarity to be ranked as a fine precious gemstone. None-the-less, rock crystal is in wide use as a gemstone due to its beauty, affordability, availability, and ease of cutting.
The most common use for rock crystal is in ornamental carvings. A well known ornamental carving for rock crystal is the crystal ball of fortune telling fame. While rock crystal is common it is hard to find large crystals of quartz with the clarity and size required for the crystal balls that most of us associate with fortune tellers. Rock crystal is used for many ornamental carvings from spheres (crystal balls) to pyramids to obelisks to figurines to eggs to bowls to wands. There are also many fine chandeliers that are outfitted with rock crystal ornaments.
Rock crystal can have the colorless clarity of pure water, unlike ordinary window glass which is a pale green. Yet the most common flaws - internal fractures - result in veils and colorful refractions that lend beauty to an otherwise ordinary object.
Rock crystal is an alternate and traditional birthstone for the month of April. Quartz is often associated with balance, clarity, and energy.
Many people prefer uncut clusters of rock crystal. These natural treasures look like crystal cities of fantasy stories. The long slender clear prisms of quartz projecting upward from a common base are true mineralogical wonders that can be admired by all. They cost of good clusters of rock crystal is quite affordable and comes from sources around the world. The best rock crystal sources are in the famous Hot Springs area of Arkansas, USA; Cumberland, England; St. Gotthard, Switzerland; Brazil and Madagascar. Large individual crystals of quartz have been found in Brazil, the largest weighs over 44 tons.
Phantoms are a result of inclusions which occur when other minerals such as chlorite, hematite or even milky quartz form as a crust on the surface of the crystals during a hiatus in the crystal's growth. The crystal then grows out and around the encrusting growth, encasing it inside. But since the thin encrustations formed over a crystal complete with crystal faces it appears that there is a crystal inside the crystal. The encrustations are often incomplete or diffuse and appear ghostly, hence the name phantom.
Rock crystal is only one of several quartz varieties. Other varieties that form macroscopic (large enough to see) crystals are as follows: