<P> For pure chemical elements, polymorphism is known as allotropy . For example, diamond and graphite are two crystalline forms of carbon, while amorphous carbon is a noncrystalline form . Polymorphs, despite having the same atoms, may have wildly different properties . For example, diamond is among the hardest substances known, while graphite is so soft that it is used as a lubricant . </P> <P> Polyamorphism is a similar phenomenon where the same atoms can exist in more than one amorphous solid form . </P> <P> Crystallization is the process of forming a crystalline structure from a fluid or from materials dissolved in a fluid . (More rarely, crystals may be deposited directly from gas; see thin - film deposition and epitaxy .) </P> <P> Crystallization is a complex and extensively - studied field, because depending on the conditions, a single fluid can solidify into many different possible forms . It can form a single crystal, perhaps with various possible phases, stoichiometries, impurities, defects, and habits . Or, it can form a polycrystal, with various possibilities for the size, arrangement, orientation, and phase of its grains . The final form of the solid is determined by the conditions under which the fluid is being solidified, such as the chemistry of the fluid, the ambient pressure, the temperature, and the speed with which all these parameters are changing . </P>

What is formed by crystals and is inorganic