( Quasicrystals are an exception, see below). A crystal is a solid where the atoms form a periodic arrangement. The scientific definition of a "crystal" is based on the microscopic arrangement of atoms inside it, called the crystal structure. amorphous solids.Ĭrystals are often used in pseudoscientific practices such as crystal therapy, and, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements. Examples of amorphous solids include glass, wax, and many plastics.ĭespite the name, lead crystal, crystal glass, and related products are not crystals, but rather types of glass, i.e. A third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. Examples of polycrystals include most metals, rocks, ceramics, and ice.
many microscopic crystals fused together into a single solid. Most inorganic solids are not crystals but polycrystals, i.e. Įxamples of large crystals include snowflakes, diamonds, and table salt. The word crystal derives from the Ancient Greek word κρύσταλλος ( krustallos), meaning both " ice" and " rock crystal", from κρύος ( kruos), "icy cold, frost". The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification. The scientific study of crystals and crystal formation is known as crystallography. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. 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.Ī crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.
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