Cristals, Black Little Rock, Somting Royalty-Free Stock Photo

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 constituents such as atoms, molecules, or ions are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.[1][2] In addition, macroscopic single crystals are usually identifiable by their 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.