The UnMuseum - Crystals Amethyst is violet quartz crystal. They can be as common as table salt, as numerous as grains on a beach, or as rare as diamonds. They are crystals. The smallest particle of any substance is called a molecule. Each molecule, in turn, is composed of one or more atoms.
Atoms are the smallest particle of an element.
An element is one of a hundred or so materials that can be combined with other elements to make all the substances in the universe. The molecules in a gas or liquid bounce or flow around each other freely. When the material changes into a solid state, the molecules lock together. As they do, they link to one another in a uniform pattern that is repeated over and over. The result is known as a crystal.