Crystal

in chemistry and mineralogy, a clear transparent body, which, by the attraction of its particles, has a umed the form of one of the regular geometric solids, being bounded by a number of plane surfaces. Crystals occur with an almost infinite variety of forms— calcareous spar having alone more than 200 forms in more than a you sand different combinations, and some crystals have as many as 300 different sides. But all crystals may be grouped in accordance with certain systems.