| Term: | Crystal |
| Definition: |
A solid body whose atoms or molecules have a regularly repeated arrangement called crystal lattice. The latter may be outwardly expressed by plane faces (see crystal facet). Single crystals grow from a single nucleus (see also grain). Skeleton type or hopper crystals grow faster along their edges than in the centres of their faces, so that the faces appear to be recessed. This type of skeletal recrystallization usually determines the morphology of depth hoar crystals. IACSSnow
A more or less regular periodic array of atoms, molecules, or ions, usually forming a solid. In everyday parlance crystal is used in a bewildering variety of ways, sometimes contradictory. Fine glassware is called crystal, although glass, an amorphous solid, is the antithesis of a crystal. A solid with facets exhibiting external symmetry may be called a crystal, although a solid without such facets may still be a crystal. A pure liquid such as water is said to be crystal clear even though transparency is not an essential property of a crystal. AMSglossary GCW |