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Crystal
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This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2012)
A crystal of amethyst quartz.
Microscopically, a single crystal has atoms in a near-perfect periodic arrangement; a polycrystal is composed of many microscopic crystals (called "crystallites" or "grains"); and an amorphous solid (such as glass) has no periodic arrangement even microscopically.
A crystal or crystalline solid is a solid material whose constituent atoms, molecules or ions et cetera are arranged in an ordered pattern extending in all three spatial dimensions. In addition to their microscopic structure, large crystals are usually identifiable by their macroscopic geometrical shape, consisting of flat faces with specific, characteristic orientations.The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.The word crystal is derived from the Ancient Greek word ???sta???? (krustallos), meaning both “ice” and “rock crystal”, from ????? (kruos), "icy cold, frost".Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most metals, rocks, ceramics, and ice. A third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass, wax, and many plastics.
^ ???sta????, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
^ ?????, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
^ "Kreus". The American Heritage Dictionary of the English Language: Fourth Edition: Appendix I: Indo-European Roots. 2000.
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System
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