A mineral solid, usually with regular angles and faces.
A chemical formation of hard regular-shaped solids.
A solid in which atoms are arranged in a specific symmetrical pattern, forming distinct lattices, with definable fixed angles, faces, walls, and interatomic relationships. Examples include ice and many salts.
When discussing intensifying screens, the velocity of the screen is determined by the size of its crystals. For instance, smaller crystals result in a slower screen speed, yet offer superior radiographic definition.